Flight Duration Research Articles

Seasonal migration patterns of Siberian Rubythroat (Calliope calliope) facing the Qinghai–Tibet Plateau

BackgroundSmall songbirds respond and adapt to various geographical barriers during their annual migration. Global flyways reveal the diverse migration strategies in response to different geographical barriers, among which are high-elevation plateaus. However, few studies have been focused on the largest and highest plateau in the world, the Qinghai–Tibet Plateau (QTP) which poses a significant barrier to migratory passerines. The present study explored the annual migration routes and strategies of a population of Siberian Rubythroats (Calliope calliope) that breed on the north-eastern edge of the QTP.MethodsOver the period from 2021 to 2023, we applied light-level geolocators (13 deployed, seven recollected), archival GPS tags (45 deployed, 17 recollected), and CAnMove multi-sensor loggers (with barometer, accelerometer, thermometer, and light sensor, 20 deployed, six recollected) to adult males from the breeding population of Siberian Rubythroat on the QTP. Here we describe the migratory routes and phenology extracted or inferred from the GPS and multi-sensor logger data, and used a combination of accelerometric and barometric data to describe the elevational migration pattern, flight altitude, and flight duration. All light-level geolocators failed to collect suitable data.ResultsBoth GPS locations and positions derived from pressure-based inference revealed that during autumn, the migration route detoured from the bee-line between breeding and wintering grounds, leading to a gradual elevational decrease. The spring route was more direct, with more flights over mountainous areas in western China. This different migration route during spring probably reflects a strategy for faster migration, which corresponds with more frequent long nocturnal migration flights and shorter stopovers during spring migration than in autumn. The average flight altitude (1856 ± 781 m above sea level) was correlated with ground elevation but did not differ between the seasons.ConclusionsOur finding indicates strong, season-dependent impact of the Qinghai–Tibet Plateau on shaping passerine migration strategies. We hereby call for more attention to the unexplored central-China flyway to extend our knowledge on the environment-migration interaction among small passerines.

Qualitative analysis of the presence of gaze-evoked nystagmus in astronauts after long term space flights. Results of “field test” experiment

In the first days after a spaceflight (SF), re-entry motion sickness and motor coordination problems reflect the need to readapt back to the natural gravitational state. Gravity is a natural stimulus for the receptors of vestibular apparatus, which plays an important role in multisensory interactions. Changes indicating an increase in excitability of the vestibular apparatus during SF (Kornilova et al., 2017) suggest a high probability of the occurrence of gaze-evoked nystagmus after prolonged SF. Russian-American experiment “Field Test” included a nystagmus test. 22 ISS crewmembers (14 Russian cosmonauts and 8 astronauts; flight duration 159.8 ± 19.5 days) participated in the experiment. The study was conducted twice before flight and several times after flight, starting within 3 h after landing. In a seated position, astronauts tracked with their eyes only (without moving their head) horizontal and vertical movements of the researcher's finger from the central position to the gaze end points (right, left, upper). Eye movements were recorded with a video camera. The videos were analyzed qualitatively for presence of nystagmus. Preflight, gaze-evoked nystagmus was detected in 5 people, the greatest changes were observed on landing day. 10 crewmembers exhibited nystagmus in the extreme left gaze position and 13 crewmembers – in the extreme right gaze position (partial recovery was observed 1–4 days after SF). A noticeable decrease in the frequency of manifestation of the nystagmus was observed only 10–13 days after landing (n = 16). Gaze-evoked nystagmus is usually considered a clinical sign of cerebellar alterations. However, it is often described in healthy people with a prevalence of up to 21 %. In a similar study involving 18 astronauts, participants of long-term SF, the frequency of occurrence of gaze-evoked nystagmus also increased in the first hours after SF (Reschke, Good and Clement, 2017). However, in this study, a detailed analysis of the presence of nystagmus in various directions was conducted for the first time. Of particular interest is the frequent detection of a gaze-evoked nystagmus in the right position after SF - this phenomenon may be a sign of presence of a central vestibular imbalance (Robinson et al., 1984), which also occurs in patients with cerebellar disorders (Bayer and Dietrich, 2011). The results allow us to expand our understanding of the severity and frequency of vestibular disorders and the dynamics of their recovery after prolonged SF.

The Future of Unmanned Aerial Vehicles (UAVs) Has No Batteries

Unmanned Aerial Vehicles (UAVs) hold immense potential across various fields, including precision agriculture, rescue missions, delivery services, weather monitoring, and many more. Despite this promise, the limited flight duration of current UAVs stands as a significant obstacle to their widespread adoption. Attempting to extend flight time by solar panel charging during midflight is not viable due to battery limitations and the eventual need for replacement. This article highlights exciting efforts towards the future of a UAV that survives in the air by harvesting solar energy and performing long-term missions without battery re-charging and/or replacement.

An Internal Marking Method for Adult Spodoptera frugiperda Smith Using an Artificial Diet Containing Calco Oil Red N-1700.

As a migratory invasive pest, Spodoptera frugiperda (fall armyworm, FAW) has recently posed a serious threat to food security in newly invaded areas (especially in Africa and Asia). Understanding its migration (or dispersal) patterns in newly invaded areas is crucial for regional forecasting and management efforts. By screening an appropriate marking technique to conduct mark-release-recapture (MRR) experiments, the migration patterns of the FAW can be effectively studied. In this study, we added different concentrations of Calco Oil Red N-1700 (an oil-soluble marker) to a self-made artificial diet and assessed the rearing and marking efficacy. The results indicated that a concentration of 0.2% of Calco Oil Red N-1700 in the diet was optimal for marking adult FAWs. The biological indicators (e.g., developmental duration, reproductive parameters, and flight ability) of FAWs fed this diet were basically consistent with those of FAWs fed a normal diet, with a larval stage of 15.46 days, a pupal stage of 9.81 days, a pupal mass of 278.18 mg, an adult longevity of 15.41 days, and an egg deposition count of 1503.51. Meanwhile, the flight distance, duration, and velocity were 24.91 km, 7.16 h, and 3.40 km/h, respectively (12 h tethered-flight tests), without difference with the control. Females and males exhibited distinctive marking colors (red or pink) that persisted for at least 5 and 9 days, respectively. This study developed an economically effective internal marking method for the adult FAW, laying the foundation for conducting MRR experiments. This will help clarify the migration behavior and routes of the FAW, providing a scientific basis for formulating effective pest management strategies.

Research on insect-like long endurance hovering double-wing FMAV prototype

PurposeEndurance time is an important factor limiting the progress of flapping-wing aircraft. In this study, this paper developed a prototype of a double-wing flapping-wing micro air vehicle (FMAV) that mimics insect-scale flapping wing for flight. Besides, novel methods for optimal selection of motor, wing length and battery to achieve prolonged endurance are proposed. The purpose of this study is increasing the flight time of double-wing FMAV by optimizing the flapping mechanism, wings, power sources, and energy sources.Design/methodology/approachThe 20.4 g FMAV prototype with wingspan of 21.5 cm used an incomplete gear flapping wing mechanism. The motor parameters related to the lift-to-power ratio of the prototype were first identified and analyzed, then theoretical analysis was conducted to analyze the impact of wing length and flapping frequency on the lift-to-power ratio, followed by practical testing to validate the theoretical findings. After that, analysis and testing examined the impact of battery energy density and efficiency on endurance. Finally, the prototype’s endurance duration was calculated and tested.FindingsThe incomplete gear facilitated 180° symmetric flapping. The motor torque constant showed a positive correlation with the prototype’s lift-to-power ratio. It was also found that the prototype achieved the best lift-to-power ratio when using 100 mm wings.Originality/valueA gear-driven flapping mechanism was designed, capable of smoothly achieving 180° symmetric flapping. Besides, factors affecting long-duration flight – motor, wings and battery – were identified and a theoretical flight duration analysis method was developed. The experimental result proves that the FMAV could achieve the longest hovering time of 705 s, outperforming other existing research on double-wing FMAV for improving endurance.

Sunlight-powered sustained flight of an ultralight micro aerial vehicle.

Limited flight duration is a considerable obstacle to the widespread application of micro aerial vehicles (MAVs)1-3, especially for ultralightweight MAVs weighing less than 10 g, which, in general, have a flight endurance of no more than 10 min (refs. 1,4). Sunlight power5-7 is a potential alternative to improve the endurance of ultralight MAVs, but owing to the restricted payload capacity of the vehicle and low lift-to-power efficiency of traditional propulsion systems, previous studies have not achieved untethered sustained flight of MAVs fully powered by natural sunlight8,9. Here, to address these challenges, we introduce the CoulombFly, an electrostatic flyer consisting of an electrostatic-driven propulsion system with a high lift-to-power efficiency of 30.7 g W-1 and an ultralight kilovolt power system with a low power consumption of 0.568 W, to realize solar-powered sustained flight of an MAV under natural sunlight conditions (920W m-2). The vehicle's total mass is only 4.21 g, within 1/600 of the existing lightest sunlight-powered aerial vehicle6.

Evaluation of the Potential Flight Ability of the Casuarina Moth, Lymantria xylina (Lepidoptera: Erebidae).

Lymantria xylina Swinhoe (Lepidoptera: Erebidae) is a potentially invasive pest, similar to Lymantria dispar asiatica Vnukovskij and Lymantria dispar japonica Motschulsky (Lepidoptera: Erebidae). To evaluate its potential for spread and flight distance related to egg deposition on vessels at ports, we employed a flight mill to assess the flight capabilities of its adults under varying conditions. Our findings revealed that females primarily flew short distances and ceased flying after 3:00 AM, whereas males covered much longer distances throughout the day. Sex, age, and flight duration significantly influenced flight ability. Females exhibited weaker flight capability than males, and their ability declined with increasing age or flight duration. Notably, 1-day-old moths displayed the strongest flight ability, with average flight distances of up to 3.975 km for females and 8.441 km for males. By the fifth day, females no longer flew, and males experienced reduced flight ability. After continuous hanging for 16 h, females lost most of their flight capacity, while males remained capable of flight even after 32 h. Additionally, female flight ability decreased significantly after mating, possibly due to factors such as egg-carrying capacity, weight, and load ratio. This study provides a foundation for assessing the risk of long-distance dispersal of L. xylina via ocean-going freighters, considering female moths' phototactic flight and oviposition.

Optimizing Forest Surveillance: A Hybrid Algorithm Combining ACO and ABC

This work introduces a potential Hybrid Algorithm for the complex field of forest monitoring, integrating Artificial Bee Colony Optimisation (ABC) and Ant Colony Optimisation (ACO). The performance indicators of the algorithm were carefully assessed in a fictitious use case. Its effectiveness was demonstrated by a shorter drone path, a shorter flight duration, and less energy usage, making it an affordable surveillance option. In addition, the algorithm demonstrated a great rate of mission coverage, quick convergence, and consistently good quality of solutions. Its usefulness in dynamic forest habitats was highlighted by its capacity to adjust to changing weather conditions and scale to accommodate more waypoints. Its cost-effectiveness is increased by efficient resource utilisation, which is demonstrated by low CPU and memory consumption. Taken together, these results highlight how the algorithm may transform forest surveillance by increasing operational effectiveness, cutting expenses, and satisfying the changing requirements of intricate monitoring scenarios. To fully realise the algorithm's potential for environmental monitoring applications, this research advocates for more real-world testing and optimisation.

Quantitative risk assessment for the introduction of bluetongue virus into mainland Europe by long-distance wind dispersal of Culicoides spp.: A case study from Sardinia.

Europe faces regular introductions and reintroductions of bluetongue virus (BTV) serotypes, most recently exemplified by the incursion of serotype 3 in the Netherlands. Although the long-distance wind dispersal of the disease vector, Culicoides spp., is recognized as a virus introduction pathway, it remains understudied in risk assessments. A Quantitative Risk Assessment framework was developed to estimate the risk of BTV-3 incursion into mainland Europe from Sardinia, where the virus has been present since 2018. We used an atmospheric transport model (HYbrid Single-Particle Lagrangian Integrated Trajectory) to infer the probability of airborne dispersion of the insect vector. Epidemiological disease parameters quantified the virus prevalence in vector population in Sardinia and its potential first transmission after introduction in a new area. When assuming a 24h maximal flight duration, the risk of BTV introduction from Sardinia is limited to the Mediterranean Basin, mainly affecting the southwestern area of the Italian Peninsula, Sicily, Malta, and Corsica. The risk extends to the northern and central parts of Italy, Balearic archipelago, and mainland France and Spain, mostly when maximal flight duration is longer than 24h. Additional knowledge on vector flight conditions and Obsoletus complex-specific parameters could improve the robustness of the model. Providing both spatial and temporal insights into BTV introduction risks, our framework is a key tool to guide global surveillance and preparedness against epizootics.

Age dominates flight distance and duration, while body size shapes flight speed in Bombus terrestris L. (Hymenoptera: Apidae).

Flight plays a crucial role in the fitness of insect pollinators, such as bumblebees. Despite their relatively large body size compared with their wings, bumblebees can fly under difficult ambient conditions, such as cooler temperatures. While their body size is often positively linked to their foraging range and flight ability, the influence of age remains less explored. Here, we studied the flight performance (distance, duration and speed) of ageing bumblebee workers using tethered flight mills. Additionally, we measured their intertegular distance and dry mass as proxies for their body size. We found that the flight distance and duration were predominantly influenced by age, challenging assumptions that age does not play a key role in foraging and task allocation. From the age of 7 to 14 days, flight distance and duration increased sixfold and fivefold, respectively. Conversely, the body size primarily impacted the maximum and average flight speed of workers. Our findings indicate that age substantially influences the flight distance and duration in bumblebee workers, affecting foraging performance and potentially altering task allocation strategies. This underscores the importance of considering individual age and physiological changes alongside body size/mass in experiments involving bumblebee workers.

Optimisation of Water Volume Consumption in Commercial Aircraft

This research paper focuses on optimising water volumes consumed in commercial aircraft water tanks during flying to reduce fuel consumption and promote sustainability. The study employs a methodology that includes real data collection, statistical analysis, and optimisation using the Response Surface Methodology (RSM). The data obtained from Boeing 787-9 and 787-10 fleets used in this study spans from December 2022 to March 2023. The findings and analyses are based on various parameters such as water usage, flight duration, and passenger count. Statistical comparisons between the water usage optimised by RSM and the present estimation model developed by the International Air Transport Association (IATA) and Boeing methods are conducted, highlighting the superior performance of RSM in terms of lower percentage errors and better optimisation. The frequency distributions of percentage errors provide further support for the effectiveness of RSM. This research significantly contributes to our understanding of optimising aircraft water usage for improved fuel efficiency and sustainability. The findings have important implications for the aviation industry and environmental preservation. By reducing fuel consumption through optimised water volumes, airlines can enhance operational efficiency while minimising environmental impact.

Effect of wind on quadrotor battery consumption

PurposeThe advancements in battery technologies, while trailing behind technological progress, face challenges meeting the soaring energy demands of quadrotors, resulting in flight durations that are far from satisfactory. Hence, this study aims to empirically investigate the impact of wind on battery consumption.Design/methodology/approachFlight tests were conducted using the Pixhawk 4 along identical flight paths and durations. In these flight tests, the quadrotor was exposed to different wind speeds.FindingsThe amount of energy consumed in the flight tests was examined. It has been observed that wind poses a serious threat to battery consumption and thus flight safety.Practical implicationsIt is predicted that the data obtained from these studies will be useful in the battery and route selection of quadrotors used in many areas in the future.Originality/valueThis experimental investigation involved conducting numerous flight trials at diverse wind speeds under genuine atmospheric conditions. The energy consumption data acquired holds significance as it directly mirrors real-world scenarios encountered in practical applications.

Weightlessness leads to an increase granulosa cells in the growing follicle

The participation of women in space programs of increasing flight duration requires research of their reproductive system from the perspective of subsequent childbearing and healthy aging. For the first time, we present hormonal and structural data on the dynamics of recovery after a 157-day space flight in a woman of reproductive age. There were no clinically significant changes in the reproductive system, but detailed analysis shows that weightlessness leads to an increase in the proportion of early antral follicles and granulosa cells in large antral follicles. Returning to Earth’s gravity reduces the number and diameter of early antral follicles.

Development of a Cost-Effective UAV for Extended Duration Disaster Management Operations using Expanded Polystyrene

Commercial UAVs specifically developed for disaster management purposes are frequently priced at an exorbitant level. Usually, unmanned aerial vehicles (UAVs) have a flight length of 15-30 minutes. However, crisis management operations often demand longer mission durations, occasionally in difficult weather circumstances. In order to tackle this problem, Expanded Polystyrene (EPS) was selected as the material for the body and wings of the UAV due to its cost-effectiveness in comparison to materials such as fiberglass, carbon fibre, epoxy, Kevlar, and wooden balsa. The EPS material utilized exhibits a tensile strength of 88 pounds per square inch (psi). For flight testing, a LiPo 3S battery with a voltage of 11.1 volts was used in the UAV. The virtual wind tunnel test was carried out with precise parameters, including an air density of 1.225 kg/m³ and a wind speed of 50 m/s. In order to improve the wing's structural integrity, a lightweight aluminium bar was incorporated. The initial design of the UAV wing showcased an elongated glider-like structure, enabling prolonged flight durations using a solitary propeller. The simulation findings showed that the UAV successfully controlled the drag coefficient with time, maintaining a traction force of 200N during testing. The UAV's capacity to endure gusts of up to 70 knots, achieve elevations of 5000 feet, and travel lengths of up to 90 km was demonstrated in practical trials, contingent upon the control systems employed. Ultimately, the newly designed UAV has the capability to sustain flight for a duration of 8 hours, thereby overcoming the constraints typically encountered with commercial UAVs employed in disaster management.

Adaptive Scheduling of High-Availability Drone Swarms for Congestion Alleviation in Connected Automated Vehicles

The Intelligent Transportation System (ITS) serves as a pivotal element within urban networks, offering decision support to users and connected automated vehicles (CAVs) through comprehensive information gathering, sensing, device control, and data processing. Presently, ITS predominantly relies on sensors embedded in fixed infrastructure, notably Roadside Units (RSUs). However, RSUs are confined by coverage limitations and may encounter challenges in prompt emergency responses. On-demand resources, such as drones, present a viable option to supplement these deficiencies effectively. This paper introduces an approach where Software-Defined Networking (SDN) and Mobile Edge Computing (MEC) technologies are integrated to formulate a high-availability drone swarm control and communication infrastructure framework, comprising the cloud layer, edge layer, and device layer. Drones confront limitations in flight duration attributed to battery limitations, posing a challenge in sustaining continuous monitoring of road conditions over extended periods. Effective drone scheduling stands as a promising solution to overcome these constraints. To tackle this issue, we initially utilized Graph WaveNet, a specialized graph neural network structure tailored for spatial-temporal graph modeling, for training a congestion prediction model using real-world dataset inputs. Building upon this, we further propose an algorithm for drone scheduling based on congestion prediction. Our simulation experiments using real-world data demonstrate that, compared to the baseline method, the proposed scheduling algorithm not only yielded superior scheduling gains but also mitigated drone idle rates.

Reinforcement learning based autonomous multi-rotor landing on moving platforms

Multi-rotor UAVs suffer from a restricted range and flight duration due to limited battery capacity. Autonomous landing on a 2D moving platform offers the possibility to replenish batteries and offload data, thus increasing the utility of the vehicle. Classical approaches rely on accurate, complex and difficult-to-derive models of the vehicle and the environment. Reinforcement learning (RL) provides an attractive alternative due to its ability to learn a suitable control policy exclusively from data during a training procedure. However, current methods require several hours to train, have limited success rates and depend on hyperparameters that need to be tuned by trial-and-error. We address all these issues in this work. First, we decompose the landing procedure into a sequence of simpler, but similar learning tasks. This is enabled by applying two instances of the same RL based controller trained for 1D motion for controlling the multi-rotor’s movement in both the longitudinal and the lateral directions. Second, we introduce a powerful state space discretization technique that is based on i) kinematic modeling of the moving platform to derive information about the state space topology and ii) structuring the training as a sequential curriculum using transfer learning. Third, we leverage the kinematics model of the moving platform to also derive interpretable hyperparameters for the training process that ensure sufficient maneuverability of the multi-rotor vehicle. The training is performed using the tabular RL method Double Q-Learning. Through extensive simulations we show that the presented method significantly increases the rate of successful landings, while requiring less training time compared to other deep RL approaches. Furthermore, for two comparison scenarios it achieves comparable performance than a cascaded PI controller. Finally, we deploy and demonstrate our algorithm on real hardware. For all evaluation scenarios we provide statistics on the agent’s performance. Source code is openly available at https://github.com/robot-perception-group/rl_multi_rotor_landing.

Seasonal patterns and processes of migration in a long-distance migratory bird: energy or time minimization?

Optimal migration theory prescribes adaptive strategies of energy, time or mortality minimization. To test alternative hypotheses of energy- and time-minimization migration we used multisensory data loggers that record time-resolved flight activity and light for positioning by geolocation in a long-distance migratory shorebird, the little ringed plover, Charadrius dubius. We could reject the hypothesis of energy minimization based on a relationship between stopover duration and subsequent flight time as predicted for a time minimizer. We found seasonally diverging slopes between stopover and flight durations in relation to the progress (time) of migration, which follows a time-minimizing policy if resource gradients along the migration route increase in autumn and decrease in spring. Total flight duration did not differ significantly between autumn and spring migration, although spring migration was 6% shorter. Overall duration of autumn migration was longer than that in spring, mainly owing to a mid-migration stop in most birds, when they likely initiated moult. Overall migration speed was significantly different between autumn and spring. Migratory flights often occurred as runs of two to seven nocturnal flights on adjacent days, which may be countering a time-minimization strategy. Other factors may influence a preference for nocturnal migration, such as avoiding flight in turbulent conditions, heat stress and diurnal predators.

Screening, characterization and optimization of potential dichlorodiphenyl trichloroethane (DDT) degrading fungi

Dichlorodiphenyltrichloroethane is an organo-chlorine insecticide used for malaria and agricultural pest control, but it is the most persistent pollutant, endangering both human and environmental health. The primary aim of the research is to screen, characterize, and assess putative fungi that degrade DDT for mycoremediation. Samples of soil and wastewater were gathered from Addis Ababa, Koka, and Ziway. Fungi were isolated and purified using potato dextrose media. Matrix-Assisted Laser Desorption, Ionization, and Flight Duration The technique of mass spectrometry was employed to identify fungi. It was found that the finally selected isolate, AS1, was Aspergillus niger. Based on growth factor optimization at DDT concentrations (0, 3500, and 7000 ppm), temperatures (25, 30, and 35 °C), and pH levels (4, 7, and 10), the potential DDT-tolerant fungal isolates were investigated. A Box-Behnken experimental design was used to analyze and optimize fungal biomass and sporulation. The highest biomass (0.981 ± 0.22 g) and spore count (5.60 ± 0.32 log/mL) of A. niger were found through optimization assessment, and this fungus was chosen as a potential DDT-degrader. For DDT degradation investigations by A. niger in DDT-amended liquid media, gas chromatograph-electron capture detector technology was employed. DDT and its main metabolites, DDE and DDD, were eliminated from both media to the tune of 96–99 % at initial DDT concentrations of 1750, 3500, 5250, and 7000 ppm. In conclusion, it is a promising candidate for detoxifying and/or removing DDT and its breakdown products from contaminated environments.

Energy supply during nocturnal endurance flight of migrant birds: effect of energy stores and flight behaviour

BackgroundMigrating birds fly non-stop for hours or even for days. They rely mainly on fat as fuel complemented by a certain amount of protein. Studies on homing pigeons and birds flying in a wind-tunnel suggest that the shares of fat and protein on total energy expenditure vary with flight duration and body fat stores. Also, flight behaviour, such as descending flight, is expected to affect metabolism. However, studies on free flying migrant birds under natural conditions are lacking.MethodsOn a Swiss Alpine pass, we caught three species of nocturnal migrant passerines out of their natural migratory flight. Since most night migrants start soon after dusk, we used time since dusk as a measure of flight duration. We used plasma concentrations of metabolites of the fat, protein, and carbohydrate metabolism as indicators of relative fuel use. We used flight altitudes of birds tracked with radar and with atmospheric pressure loggers to characterize flight behaviour.ResultsThe indicators of fat catabolism (triglycerides, very low-density lipoproteins, glycerol) were positively correlated with body energy stores, supporting earlier findings that birds with high fat stores have a higher fat catabolism. As expected, plasma levels of triglycerides, very low-density lipoproteins, glycerol and ß-hydroxy-butyrate increased at the beginning of the night, indicating that nocturnal migrants increased their fat metabolism directly after take-off. Surprisingly, fat catabolism as well as glucose levels decreased in the second half of the night. Data from radar observations showed that the number of birds aloft, their mean height above ground and vertical flight speed decreased after midnight. Together with the findings from atmospheric pressure-loggers put on three species, this shows that nocturnal migrants migrating over continental Europe descend slowly during about 1.5 h before final landfall at night, which results in 11–30% energy savings according to current flight models.ConclusionsWe suggest that this slow descent reduces energy demands to an extent which is noticeable in the plasma concentration of lipid, protein, and carbohydrate metabolites. The slow descent may facilitate the search for a suitable resting habitat and serve to refill glycogen stores needed for foraging and predator escape when landed.

The Risk of Aircraft-Acquired SARS-CoV-2 Transmission during Commercial Flights: A Systematic Review.

The aircraft-acquired transmission of SARS-CoV-2 poses a public health risk. Following PRISMA guidelines, we conducted a systematic review and analysis of articles, published prior to vaccines being available, from 24 January 2020 to 20 April 2021 to identify factors important for transmission. Articles were included if they mentioned index cases and identifiable flight duration, and excluded if they discussed non-commercial aircraft, airflow or transmission models, cases without flight data, or that were unable to determine in-flight transmission. From the 15 articles selected for in-depth review, 50 total flights were analyzed by flight duration both as a categorical variable-short (<3 h), medium (3-6 h), or long flights (>6 h)-and as a continuous variable with case counts modeled by negative binomial regression. Compared to short flights without masking, medium and long flights without masking were associated with 4.66-fold increase (95% CI: [1.01, 21.52]; p < 0.0001) and 25.93-fold increase in incidence rates (95% CI: [4.1, 164]; p < 0.0001), respectively; long flights with enforced masking had no transmission reported. A 1 h increase in flight duration was associated with 1.53-fold (95% CI: [1.19, 1.66]; p < 0.001) increase in the incidence rate ratio (IRR) of cases. Masking should be considered for long flights.