Crash rates of scheduled commuter and air carrier flights before and after a regulatory change.

Throughout the period 1977–1994, scheduled commuter flights had far higher crash rates than major airlines (3,8,9). The safety record of commuter aircraft has long been of concern (11). In the early 1990s, Baker and colleagues described the circumstances of commuter crashes during 1983–88 and suggested that commuter flights should be subject to some of the stricter safety standards that protect passengers flying on Part 121 airlines (1,2). In 1994, the National Transportation Safety Board (NTSB) published the findings of a study of commuter airline safety and recommended that the FAA revise its regulations so that the provisions of Part 121 would be applied to all scheduled service in aircraft with 20 or more passenger seats and, wherever feasible, to aircraft with 10–19 seats (12). The NTSB based its recommendations on findings regarding Part 135 practices, including the following: flight time and crew rest regulations had resulted in many commuter pilots flying when fatigued; the short periods of time between flights increased the risk that pilots would make critical mistakes in planning for the next flight; many airlines failed to provide adequate training in crew resource management; and newly trained pilots might not be adequately trained. For decades, scheduled flights of aircraft with > 30 passenger seats have been subject to Part 121 regulations. In 1995 the FAA published new requirements for commuter operations (7) in response to the high crash rates of Part 135 flights and the NTSB recommendations (12), as well as to several highly publicized fatal crashes of commuters with 10–30 seats in 1993–94 (10). The new rule stated that after March 20, 1997, all scheduled flights of aircraft with 10–30 passenger seats would be required to operate under Part 121 rules (7) (aircraft with 10–30 passenger seats are primarily turboprops, unlike the larger turbojet aircraft that have always been subject to Part 121 rules). A decade of data on flight operations and crashes since 1997 is now available, but has not been used to evaluate the effect of the rule change. A major reason for failure to examine the trend is that the FAA and NTSB categorize and publish the numbers of scheduled flight departures and crashes not by aircraft size but by whether they are governed by Part 135 or Part 121 rules. Prior to 1997, published data on departures and crashes of Part 135 flights combined aircraft having 10–30 passenger seats with aircraft having < 10 passenger seats; after 1997, crashes and departures of aircraft with 10–30 seats could not be separated from crashes and departures of aircraft with more than 30 passenger seats because they were combined in Part 121 data. Whether there was any change in crash rates of aircraft with 10–30 seats—the operations that were the focus of the rule change—could not be determined from the published data. This paper determines and reports crash rates of three categories of scheduled aircraft flights—those with 30 passenger seats—before and after the rule change. Our primary objective was to identify any apparent effect of the regulatory change on aircraft with 10–30 seats, since these flights were specifically targeted by the FAA rule change. Additional objectives were to determine trends in crash rates of all scheduled flights, categorized by size—i.e., the number of passenger seats.