About the data
Data for this project was assembled from a variety of databases maintained by the Federal Aviation Administration, the National Transportation Safety Board and the Bureau of Transportation Statistics.
- Data on airline crashes and incidents comes from the NTSB's accident database. Only accidents and incidents involving scheduled passenger aircraft flying for airlines certified exclusively under Chapter 121 are included. This designation includes passenger flights with 10 or more seats; however, airlines that operate both under Chapter 121 and under Chapter 135 (flying planes with less than 10 seats) have been excluded.
- Information about airline operators, and the business names they use, is from the FAA's air operators database.
- Traffic data for the month of June, 2009 is from the Bureau of Transportation Statistics' T-100 database, specifically, the systemwide segment data for US carriers. For more about these reports see here. These records report all passenger traffic for Large Certificated Air Carriers, Small Certificated Air Carriers and Commuter Air Carriers, however, only airlines operating under Chapter 121 were considered for safety analysis. The numbers reflect flight segments (rather than paying customers), so a trip from New York to Los Angeles with a layover in Denver would be counted as two trips.
- Information about branded partnerships, and unbranded affiliates is from the Regional Airline Associations 2009 Annual Report.
The FAA and the BTS rely on two different coding schemes for airlines. The NTSB's accident database uses the FAA's coding scheme in identifying the operator of a flight. In many cases, however, that code is missing or misspelled. Researchers at The Investigative Reporting Workshop reviewed records of all airline crashes and incidents that occurred between 2002 and late 2009, and identified the correct FAA designator code, as well as the corresponding BTS identification number.
Regional versus Major
A regional is an airline that flies planes with an average seating capacity of fewer than 100 and that operates under Part 121 of FAA regulations. A major is an airline that flies planes with an average of more than 100 passengers and operates under Part 121 of FAA regulations.
The FAA licenses airlines on the basis of the planes they fly. Regularly scheduled passenger planes with fewer than 10 seats are flown under Chapter 135, while larger scheduled passenger planes fly under Chapter 121. Small carriers that operate planes under both chapters may be jointly certified. In this project we only considered airlines operated exclusively under Chapter 121 to be regional, and excluded smaller local carriers. Therefore, the total percent of flights operated by major and regional carriers will not add to 100.