Data concerning the growth and utilization of regional jets between 1998 and 2003 are presented and analyzed. During this period, daily regional jet operations increased by 356%. These additional flights were primarily used to enter new midrange markets that were previously too far to serve efficiently with a turboprop and too small to warrant a traditional jet. Analysis of aircraft situational display to industry operational data also shows an increase in the stage length of regional jet flights; for example, at Dallas‐Fort Worth, the regional jet catchment basin increased from 299 n mile to 868 n mile. To better understand the reasons for the rapid growth of regional jets, an analysis of the economics of regional flight was performed. This analysis shows that airlines benefit from regional jets primarily because of the fee-per-departure payment structure and their current utilization patterns. HE number of regional jets in the national airspace system (NAS) has grown significantly over the past 10 years. Regional jets are small, 30‐100 seat aircraft capable of flying up to 1000 n mile and have been growing in number at a nearly exponential rate since 1994 (Ref. 1). This increase represents a major change in the composition of the national fleet and may affect the efficiency of the air traffic control system, as well as the dynamics of the airline industry. This paper examines the evolution of regional jet utilization to better understand their growth and operating patterns, as well as possible future trends. The goal just outlined was reached in two steps. The first was to analyze flight track data and develop methods to visualize and quantify any changes in the flight patterns of regional jets. Once this was accomplished, the second step was to analyze aircraft economics, aircraft utilization, airline scope clause agreements, and other factors to develop an understanding and explanation of the observed patterns. II. Methodology A. Data Sources To perform an analysis of emerging regional jet trends and compare them to those of other aircraft, this study made use of actual flight data from the aircraft situational display to industry (ASDI) feed. The ASDI feed provides aircraft position and speed information during flight, in addition to the flight origin, destination, and departure/arrival times. The ASDI feed is compiled from the Federal Aviation Administration’s (FAA’s) Enhanced Traffic Management System (ETMS) and is made available to vendors, who can then pass the data on to other interested parties. This study used ASDI data for one Thursday in January, between 1998 and 2003, resulting in a total of 6 days. Each data sample is from the same month and weekday to eliminate the effects of seasonal and weekly variations in airline operations. The specific dates were chosen to represent typical January days. In particular,