Short-haul Flights Research Articles

In-Flight UV-A Exposure of Commercial Airline Pilots.

INTRODUCTION: Understanding UV exposure is essential for the assessment of its contribution to the occupational risk of pilots developing ocular and skin pathologies. The objective of this observational study was to measure the UV exposure of pilots flying between the United Kingdom and a range of destinations at three different seasons.METHODS: The in-flight UV exposure of pilots was measured on 322 Monarch Airlines short-haul flights on the Airbus A321-231 and Airbus A320-214 to 31 destinations, mostly in Europe, from 4 UK airports in September 2016-August 2017. The erythema effective and UV-A doses were compared with the ICNIRP guidance and typical recreational weekend exposure of UK office workers.RESULTS: The erythema effective radiant doses did not exceed 0.1 SED. For most of the flights, the UV-A exposure was also low. On 27 single sector flights, UV-A exposure could have exceeded the ICNIRP guidance if eye protection was not used.DISCUSSION: The UV exposure in a cockpit is mostly governed by the presence of direct sunlight and the duration of a flight. The average monthly exposures were low and significantly below weekend recreational exposures of UK office workers over a similar period. To assess the contribution of occupational UV exposure to the risk of developing sun-related ocular and cutaneous pathologies, it is important to consider the accumulative flight time, destinations, and UV attenuation of aircraft windshields. Additionally, leisure and recreational outdoor time needs to be considered before meaningful overall risk analysis can be undertaken.Baczynska KA, Brown S, Chorley AC, O'Hagan JB, Khazova M, Lyachev A, Wittlich M. In-flight UV-A exposure of commercial airline pilots. Aerosp Med Hum Perform. 2020; 91(6):501-510.

Aircraft Takeoff Performance in a Changing Climate for Canadian Airports

Temperature and wind are major meteorological factors that affect the takeoff and landing performance of aircraft. Warmer temperatures and the associated decrease in air density in future climate, and changes to crosswind and tailwind, can potentially impact aircraft performance. This study evaluates projected changes to aircraft takeoff performance, in terms of weight restriction days and strong tailwind and crosswind occurrences, for 13 major airports across Canada, for three categories of aircraft used for long-, medium- and short-haul flights. To this end, two five-member ensembles of transient climate change simulations performed with a regional climate model, for Representative Concentration Pathway (RCP) 4.5 and 8.5 scenarios, respectively, are analyzed. Results suggest that the projected increases in weight restriction days associated with the increases in daily maximum temperatures vary with aircraft category and airfield location, with larger increases noted for airfields in the south central regions of Canada. Although avoiding takeoff during the warmest period of the day could be a potential solution, analysis focused on the warmest and coolest periods of the day suggests more weight restriction hours even during the coolest period of the day, for these airfields. Though RCP8.5 in general suggests larger changes to weight restriction hours compared to RCP4.5, the differences between the two scenarios are more prominent for the coolest part of the day, as projected changes to daily minimum temperatures occur at a much faster rate for RCP8.5 compared to RCP4.5, and also due to the higher increases in daily minimum temperatures compared to maximum temperatures. Both increases and decreases to crosswind and tailwind are projected, which suggest the need for detailed case studies, especially for those airfields that suggest increases. This study provides useful preliminary insights related to aircraft performance in a warmer climate, which will be beneficial to the aviation sector in developing additional analysis and to support climate change adaptation-related decision-making.

The prospects of hybrid-electric regional air transport - an assessment of travel time benefits of domestic short-haul flights in Germany with 19-seater aircraft

Aviation policy in the EU aims at improving connectivity and reducing environmental impacts. New propulsion systems that are locally free of emissions, e.g. with battery or hydrogen powered designs may contribute to this objective. Initial research suggests that such innovations are best applied in commuter aircraft with up to 19 seats. However, the market for these aircraft has been steadily declining since the end of the 1990s. In this paper, the authors analyze the prospects of re-vitalizing this aircraft category by applying an innovative business model, using hybrid-electric commuter aircraft designed in a cooperative project between Bauhaus Luftfahrt and the German Aerospace Center (DLR) in order to contribute to both objectives. The aircraft, based on characteristics of the BAe Jetstream 31, features a full electric range of approximately 200 km at a payload of 16 passengers, increasing to 1250 km, when the jet fuel-based range extender is used. The potential use of such a hybrid-electrically powered regional aircraft for regional air transport services from smaller airfields is demonstrated from a demand perspective. Travel time benefits are quantified alongside initial demand potentials, based on forecasts for 2030 at the regional pair level as provided by the German Federal Transport Plan.

Replacing short-haul flights with land-based transportation modes to reduce greenhouse gas emissions: The case of Finland

Even though air travel often provides the fastest transport option, it also has the highest climate impact. Especially on long-haul trips, an aircraft usually represents the only feasible option. Nevertheless, aircraft are more often used on short-haul routes as well. It is the short-haul flights that produce the highest emissions per passenger. These are also the ones that could be replaced the most easily by land-based transportation modes. This study investigates the greenhouse gas emissions reduction potential of replacing short-haul flights with train, coach and car travel within Finland while also taking into account real travel times from door to door. Our results showed that replacing short-haul flights could significantly reduce a country’s climate impact. Furthermore, we found that existing land-based transportation modes can keep up with the travel times of aircrafts on routes up to 400 km.

The effect of compression stocking on leg edema and discomfort during a 3-hour flight: A randomized controlled trial

BackgroundCompression stockings reduce the risk of thromboembolic complications, leg edema, and edema-related pain and discomfort during long-haul flights. The aim of this study was to assess if compression stockings reduce leg edema, pain, and discomfort during a three-hour flight. MethodsThis randomized controlled trial had a paired design as participants were randomized to wear a compression stocking on one leg during a three-hour flight with the other leg acting as control. Eligibility criteria were adults aged 18–60 years living in Denmark without medical indication for wearing compression stockings during flights. The primary outcome was the change in difference of ankle circumference between legs with and without compression stocking pre- and post-flight. Secondary outcomes were changes in difference of calf circumference, pain, and discomfort pre- and post-flight. All outcomes were self-reported with measurements and questionnaires. ResultsA total of 34 participants, median age 31 years (range 25–54), were randomized with complete follow-up. Difference in ankle circumference was median 5 mm larger post-flight compared with pre-flight (interquartile range (IQR) = 0–9, p = .001) and the corresponding change in calf circumference difference was median 5 mm (IQR = 1–12, p < .001). Ankle- and calf circumferences decreased in the leg wearing compression stocking and increased in the other leg. There was no change in difference of pain and discomfort and no adverse events. ConclusionCompression stockings reduced edema formation in young healthy passengers during a three-hour flight. Passengers experiencing edema-related discomfort during short-haul flights may benefit from wearing compression stockings during air travel.Trial registration: clinicaltrials.gov: NCT03546725.

Potential of integrated flight scheduling and rotation planning considering aerodynamic-, engine- and mass-related aircraft deterioration

Aircraft are subject to steady deterioration effects in flight operations resulting in increased fuel consumption due to decreased engine efficiency, increased airframe surface roughness and increased operating empty mass. These effects are taken into account in operational flight planning (e.g. fuel calculations) but long-term efficiency loss is rarely respected in flight and rotation scheduling. In most cases, each aircraft type per fleet series is treated homogeneously and scheduled considering maintenance events, equipment and other restrictions. This work investigates fuel saving potentials by additionally considering the aircraft tail sign-specific efficiency during aircraft to flight assignment. For this purpose, we calculate additional fuel consumption caused by deterioration effects, expressed as performance factor and mass deviation. By using an integrated flight scheduling and aircraft rotation model, aircraft will be reassigned to flights from given flight schedules by minimizing operating costs or fuel consumption. Our research yields in a saving of 22,400 kg fuel for 15 long-haul aircraft (150 kg per reassigned flight on average) based on a flight schedule for a typical week of an air cargo operator. The saving potential depends on the number of flight legs, their distance and the number of available aircraft, their performance variation and loading factor. Although relative savings are of theoretical nature and marginal to total fuel burn (0.2%), we propose an inexpensive approach to decrease total fuel consumption. Furthermore, we show that the usual approach of assigning less efficient aircraft to short flight legs is applicable but does not always provide in the cost minimum solution because low cruising altitudes of short-haul flights adversely affect fuel consumption.

The Negative Influence of Air Travel on Health and Performance in the National Basketball Association: A Narrative Review.

Air travel requirements are a concern for National Basketball Association (NBA) coaches, players, and owners, as sport-based research has demonstrated short-haul flights (≤6 h) increase injury risk and impede performance. However, examination of the impact of air travel on player health and performance specifically in the NBA is scarce. Therefore, we conducted a narrative review of literature examining the influence of air travel on health and performance in team sport athletes with suggestions for future research directions in the NBA. Prominent empirical findings and practical recommendations are highlighted pertaining to sleep, nutrition, recovery, and scheduling strategies to alleviate the negative effects of air travel on health and performance in NBA players.

Multicriteria Spatial Decision Analysis for the Development of the Italian Minor Airport System

The infrastructures supporting air transport throughout the world in the civil sector are classified as primary-level (large numbers of passengers and goods on both commercial and charter long- and medium-haul flights) and secondary-level (few passengers and goods on general aviation private, short-haul flights). In parallel with primary-level air traffic general growth all over the world and in Italy, the popularity of “individual” nonscheduled general aviation traffic increased in many countries since 1990s. The latter aviation has proved to be a valid alternative to rail and road transport for short-medium distance journeys (100-500 km) for classes of business and tourist passengers. In keeping with the national and international airport system development scenarios, the paper illustrates the results of in-depth analyses aiming to construct an integrated GIS-based Multicriteria Decision Analysis evaluation methodology. It gears towards formulating strategies for the development and streamlining of some existing (51) Italian minor airports and for the right locations for the new hubs required to construct an efficient second-level air transport network (the “highway in the sky”). Different levels of evaluation verify the suitability of airport services and infrastructure (status quo) and the attractiveness of airport hubs given the territorial facilities found in their catchment areas.

Fifth Freedom Traffic Rights: Formidable Threat or Theoretical Concern?

The fifth freedom right means that the aircraft of country A, from a service originating in country A, is allowed to embark passengers and cargo in country B and disembark them in country C. The fifth freedom has been controversial largely because country B and country C (and their national carriers) often view country A airlines as ‘stealing’ their own markets. Although the controversy still exists, the liberalization of market access restrictions has spread to many parts of the world and governments have granted more fifth freedom rights. Interestingly, however, the use of fifth freedom passenger rights has been decreasing. The decline of fifth freedom flights is largely due to the following factors: the availability of longer range aircraft, integrated airline partnerships and growing sixth freedom offerings. Passengers are connecting via airline partnerships, and on sixth freedom-heavy airlines. Such options can more adequately serve markets than fifth freedom operators. There are also greater third and fourth freedom short-haul flights, largely due to the development of low-cost airlines. There are some markets where fifth freedom markets are under scrutiny. Certain airlines still seek and operate fifth freedom routes in order to enlarge the market available to them. Compared to the trend, however, these are minor developments. The significance of fifth freedom traffic rights will continue to diminish.

Measured moisture accumulation in aircraft walls during simulated commercial flights

Aircraft can acquire large amounts of moisture during routine flights. Once moisture is trapped in aircraft walls, the resulting expenses are not just in extra fuel consumption, but also in corrosion repair and additional maintenance. To date, however, there is a lack of concrete data on temporal moisture accumulation and its distribution within aircraft walls. This investigation constructed reduced-scale mockups of an aircraft section for measurement of accumulated moisture during flights. The mockup models were placed in a psychrometric altitude chamber to mimic short-haul, medium-haul, and long-haul flights. For simulation of different flight conditions, the mockups varied in terms of shell material (aluminum alloy or composite plastic), insulation blankets (wrapped in water-resistant bags or not), and operating season (summer or winter). The moisture accumulation within insulation layers and on the inner skin of the shell after each flight was weighed on a digital precision balance. The results show that the bags used to wrap the insulation blankets effectively minimize moisture migration and accumulation. Moisture accumulation during flights in the winter season is much greater than in the summer season. The composite shell can minimize moisture gain, especially during the winter.

Prescriptive analytics in airline operations: Arrival time prediction and cost index optimization for short-haul flights

In this paper, we provide arrival time prediction combined with a cost index optimization model for short haul flights. Our work is based on flight data of a European network carrier. We focus on predicting the arrival time for incoming flights at two hub locations. Airlines focus on two aspects in their operations: Minimizing cost while ensuring on-time arrivals. Especially network carriers with hub connections need to ensure that incoming flights are on time for passenger, crew and aircraft transfer. The cost index is a tool for optimizing the aircraft’s speed. A high cost index implies a faster flight. The cost of time is set in relation to the cost of fuel. Today there is no model for arrival time prediction and integrated cost index optimization. We consider three different flight distances to model the impact of cost index changes on gate arrival time. With our model airlines are able to reduce the cost index without any tangible impact on their overall schedule. We conclude that the optimal cost index level heavily depends on a flight’s distance, fuel costs and delay costs. Especially for short haul flights we recommend lowering the cost index as a high cost index has limited impact on gate arrival time.

An assessment of cruise NOx emissions of short-haul commercial flights

Cruise NOx emissions of aircraft are an important input parameter for studies investigating climate change due to their ability to alter the concentrations of certain trace gases, such as ozone, methane, and hydroxyl in the atmosphere, and to induce positive radiative forcing. Therefore, it is of importance to minimize estimation errors on NOx emitted from aircraft engines at high altitude. In this study, the cruise NOx emissions of a frequently-used narrow-bodied aircraft type operating domestic flights in Turkey, are quantified based on numerous actual flight, actual emissions and actual meteorological data. The overall average cruise NOx emissions index is found to be ∼10 g/kg fuel. In addition, newly-developed parameters of the aircraft cruise NOx footprint and NOx intensity are calculated to be 0.5 g/pa-NM and ∼60 g/NM, respectively. Regarding the effects of flight parameters on cruise NOx emissions, while there is a distinct increase in NOx parameters with an increase in aircraft mass, this may differ for altitude. The results reveal that the NOx emissions index tends to increase slightly by 1–2%, particularly above 28,000 ft, whereas NOx intensity decreases at a rate of 2.4–2.7% per 2000 ft of cruise altitude increase.

Maximizing airborne delay at no extra fuel cost by means of linear holding

This paper introduces a linear holding strategy based on prior works on cruise speed reduction, aimed at performing airborne delay at no extra fuel cost, as a complementary strategy to current ground and airborne holding strategies. Firstly, the equivalent speed concept is extended to climb and descent phases through an analysis of fuel consumption and speed from aircraft performance data. This gives an insight of the feasibility to implement the concept, differentiating the case where the cruise flight level initially requested is kept and the case where it can be changed before departure in order to maximize the linear holding time. Illustrative examples are given, where typical flights are simulated using an optimal trajectory generation tool where linear holding is maximized while keeping constant the initially planned fuel. Finally, the effects of linear holding are thoroughly assessed in terms of the vertical trajectory profiles, range of feasible speed intervals and trade-offs between fuel and time. Results show that the airborne delay increases significantly with nearly 3-fold time for short-haul flights and 2-fold for mid-hauls to the cases in prior works.

0156 ADDITIVE EFFECTS OF THE NUMBER OF COMPLETED FLIGHTS AND TIME AWAKE ON FATIGUE IN SHORT-HAUL AIRLINE PILOTS

Time awake more so than the duration of the flight duty period affects airline pilots’ fatigue, consistent with current models of sleep-wake regulation. It is less clear, however, whether the quality of the time awake impacts fatigue. Although current flight time limitations take the number of flights within a duty period as a measure of workload into account, quantitative evidence for its fatiguing effect is scarce. Fatigue (Samn-Perelli 20-point scale) and workload ratings (NASA-Task-Load-Index) were obtained at the end of each of 553 short-haul flights from 37 pilots operating regular rosters. Pilots also checked off from a predefined list the hassles (e.g. critical fuel status, unforeseen aircraft change, bad weather, no break between flights etc.) experienced during each flight. A linear mixed-model with fatigue as dependent variable was adjusted for time awake, number of completed flights, number of hassles, and pilot’s responsibility (flying/monitoring). In addition, we tested (linear mixed-model) the influence of number of hassles, number of flights, time awake, and pilot’s responsibility on subjective workload. Linearity of the predictors, and absence of multicollinearity were verified. Fatigue was influenced by time awake, number of flights and pilot’s responsibility (p<0.05), whereas no effect was found for number of hassles. Fatigue increased by 0.4 points with every hour awake, and by 0.3 points with every completed flight (other variables kept constant). Fatigue was lower by 0.4 points when the pilot was flying instead of monitoring. Assuming one completed flight fatigue exceeded the critical threshold of 12 points (flying duty not recommended) after 17.1h awake, whereas with four completed flights this threshold was crossed already after 14.7h. Subjective workload increased with number of hassles, but not with number of flights or time awake. Objective workload measured by the number of completed flights contributes to fatigue, adding to the time-awake effect. Subjective workload assessed by the NASA-Task-Load-Index increases with the number of hassles, but not with the number of flights, indicating that this instrument is not sensitive to this type of objective workload. This research was supported by the Air Traffic Program of the German Aerospace Center.

The role of intrinsic in-flight cues in relationship quality and behavioural intentions: segmentation in less mindful and mindful passengers

ABSTRACTThe current study quantifies the relationship between intrinsic in-flight cues, passenger satisfaction, affective commitment, trust, and behavioural intentions in passengers travelling in low-cost carriers and legacy airlines. As far as we know, this is the first attempt to employ a multi-group analysis to test (1) if passengers in low-cost carriers and legacy airlines, and also (2) if the group of mindful passengers and the group of less mindful ones, have significantly different perceptions about flights in Europe. A total of 304 cases of legacy airlines and low-cost carriers were used in data analysis. Overall, affective commitment and trust are mainly triggered by in-flight ambience and space/function. Satisfaction and affective commitment play a more important role in behavioural intentions. As expected, the findings do not reveal significant differences associated with the paths between low-cost carriers and legacy airlines in short-haul flights in Europe. Nevertheless, compared with less mindful passengers, mindful ones tend to be more critical about in-flight attributes and do not easily develop a committed relationship.

Sleep, alertness and alertness management among commercial airline pilots on short-haul and long-haul flights

Airline pilots’ sleep and on-duty alertness are important focus areas in commercial aviation. Until now, studies pertaining to this topic have mainly focused on specific characteristics of flights and thus a comprehensive picture of the matter is not well established. In addition, research knowledge of what airline pilots actually do to maintain their alertness while being on duty is scarce.To address these gaps in research knowledge, we conducted a field study on a representative sample of the airline pilots of a medium-sized airline. The sample consisted of 90 pilots, of whom 30 flew long-haul (LH) routes, 30 short-haul (SH) routes, and 30 flew both. A total of 86 pilots completed the measurements that lasted for almost two months per pilot. The measurements resulted in a total of 965 flight duty periods (FDPs) including SH flights and 627 FDPs including LH flights. During the measurement periods, sleep was measured by a diary and actigraphs, on-duty alertness by the Karolinska Sleepiness Scale (KSS) in all flight phases, and on-duty alertness management strategies by the diary.Results showed that SH and LH FDPs covering the whole domicile night (00:00–06:00 at home base) were most consistently associated with reduced sleep-wake ratio and subjective alertness. Approximately every 3rd FDP falling into this category involved a reduced sleep-wake ratio (1:3 or lower) and every 2nd a reduced level of subjective alertness (KSS rating 8–9 in at least one flight phase). The corresponding frequencies for the SH and LH FDPs that partly covered the domicile night were every 10th and every 5th FDP and for the pure non-night FDPs every 30th and every 36th FDP, respectively. The results also showed that the pilots tended to increase the use of effective on-duty alertness management strategies (consuming alertness-promoting products and taking strategic naps) in connection with the FDPs that overlapped the domicile night. Finally, the results showed that the frequency of flights involving reduced subjective alertness depended on how alertness was assessed. If it was assessed solely in the flight phase just before starting the landing procedures (top of descent) the phenomenon was less frequent than if the preceding cruise phase was also taken into account.Our results suggest that FDPs covering the whole domicile night should be prioritised over the other FDPs in fatigue management, regardless of whether an FDP is a short-haul or a long-haul. In addition, the identification of fatigue in flight operations requires one to assess pilots’ alertness across all flight phases, not only at ToD. Due to limitations in our data, these conclusions can, however, be generalise to only LH FDPs during which pilots can be expected to be well acclimatised to the local time at their home base and SH night FDPs that include at least 3h of flying in the cruise phase.

Abstract # 1753 Markers of circadian disturbances in cabin crew: Combining cortisol and melatonin responses with self-reporting measures

The irregular work schedules of cabin crew with early starts, long working hours, night flights, and the crossing of time zones contribute to circadian stress. The paper examined the potential repercussions of circadian stress on a total of 84 cabin crew both from short haul (SH) and long haul (LH) flights through the combine the use of central circadian clock-controlled hormones cortisol and melatonin and self-reporting measures of fatigue, mood and anxiety. In addition to a more integrative assessment of fatigue and in order to inform Fatigue Management Systems in commercial airlines, measures were collected throughout a day of flight duty service (FDS). Despite the differences between LH and SH, the expected circadian rhythm for cortisol was observed, i.e., for higher values at the start of FDS and lower concentrations at the end of a FDS. The expected rhythm for melatonin was only observed for LH participants, with SH cabin crew exhibiting significantly decreased concentration of melatonin at the end of a FDS. The paper proposes the continuous exposure to artificial environmental light of SH cabin crew as the root cause for the disturbed neuroendocrine disturbances. In addition, the close crosstalk between the circadian and immune systems and the wide-ranging implications for disease as the higher incidence of cancer and the exacerbation of autoimmune symptoms in shift workers is discussed.

The influence of a low air pressure environment on human metabolic rate during short-term (< 2h) exposures.

Passengers in aircraft cabins are exposed to low-pressure environments. One of the missing links in the research on thermal comfort under cabin conditions is the influence of low air pressure on the metabolic rate. In this research, we simulated the cabin pressure regime in a chamber in which the pressure level could be controlled. Three pressure levels (101/85/70 kPa) were tested to investigate how metabolic rate changed at different pressure levels. The results show that as pressure decreased, the respiratory flow rate (RFR) at standard condition (STPD: 0°C, 101 kPa) significantly decreased. Yet the oxygen (O2 ) consumption and carbon dioxide (CO2 ) production significantly increased, as reflected in the larger concentration difference between inhaled and exhaled air. A significant increase in the respiratory quotient (RQ) was also observed. For metabolic rate, no significant increase (P>0.05) was detected when pressure decreased from 101 kPa to 85 kPa; however, the increase associated with a pressure decrease from 85 kPa to 70kPa was significant (P<0.05). Empirical equations describing the above parameters are provided, which can be helpful for thermal comfort assessment in short-haul flights.

IMPACT OF TIMETABLE SYNCHRONIZATION ON HUB CONNECTIVITY OF EUROPEAN CARRIERS

This paper evaluates the net impact of timetable synchronization on the connectivity of the key European carriers at their main hubs. We measure hub connectivity using a weighted connectivity score (WCS) that takes into account the number and the trip time related quality of flight connections. Based on WCS, we compare hub performance resulting from the existing schedule against a random expectati on calculated from multiple randomized schedule simulations. In each simulated schedule scenario we randomly vary the flight departure and arrival times within the operation hours at a hub and at outbound stations keeping all other flight parameters from the real schedule unchanged.We observe that the timetable synchronization leverages hub connectivity of most analyzed airlines by 40% to 60%. The highest increase of connectivity is achieved by medium-sized carriers that operate peaky wave systems with flights concentrated in many short and non-overlapping banks, as well as by carriers that organize their flights in directional waves. The lowest increase is achieved by airlines that operate at highly congested airports. At most hubs, connections to long-haul flights operated with wide-body aircraft are better synchronized than connections between short-haul flights.

Bacteria that Travel: The Quality of Aircraft Water.

The travelling population is increasing globally year on year. International tourist arrival figures reached 1087 million in 2013 and 1133 million in 2014; of which 53% and 54% respectively accounted for air transport. The water on board aircraft is sourced from surface or ground water; piped to a central filling point and distributed to each aircraft by water service vehicles at the home base or at the destination airport. The purpose of this study was to ascertain the microbial, chemical (pH; Total and Free chlorine) and physical (temperature) quality of water from two aircraft, long- and short-haul, as well as from the original water source and the water service vehicle. A total of 154 water samples were collected and analysed. Long-haul flights were found to be significantly poorer in terms of microbial quality than short haul flights (p = 0.015). Furthermore, correlation and regression analysis showed that the water service vehicle was a significant source of increased microbial load in aircraft. Microbial diversity was also demonstrated, with 37 bacterial species identified belonging to eight classes: γ-Proteobacteria; β-Proteobacteria; α-Proteobacteria; Bacilli; Actinobacteria; Flavobacteria; Sphingobacteria and Cytophaga; using phenotypic and 16S rDNA sequence-based analysis. We present a novel quantified study of aircraft-related potable water supplies.