1. Plane Crash Info 2017 Causes of Fatal Accidents by Decade http://www.planecrashinfo.com/cause.htm
2. Ackert , S. P. 2010 http://aircraftmonitor.com/uploads/1/5/9/9/15993320/basics_of_aircraft_maintenance_programs_for_financiers___v1.pdf
3. Reliability-Centered Maintenance
4. ATA Annual Reports 1970 A4A Passenger Cost Airline Index (1977-present)