million flights. veteran aviation safety expert john cox. what s significant about that is that we re improving by 50% over last year, which was the aviation s safest year previously. reporter: why the improvement? pilots have never been better trained. computerized cockpits monitor every aspect of flight. alert systems warn of a potential mid-air crash or mountain ahead. hd simulators for pilots and air traffic controllers train them to handle emergencies before they face a real one. debbie herzman is chairman of ntsb. we ve learned from accidents, plowed those lessons back, in they ve been embraced and we re not seeing repeats of those same accidents. reporter: experts say two accidents in which human failure was at least partly to blame underscore that remains the biggest threat to safety. air france 447 crashed into the
veteran aviation safety expert john cox. what s significant about that is that we re improving by 50% over last year, which was the aviation s safest year previously. it s an incredible feat. reporter: why the improvement? pilots have never been better trained. computerized cockpits monitor every aspect of flight. alert systems warn of a potential mid-air crash or mountain ahead. hd simulators for pilots and air traffic controllers train them to handle emergencies before they face a real one. debbie hersman is chairman of ntsb. we ve learned from accidents, plowed those lessons back in, they ve been embraced and we re not seeing repeats of those same accidents. reporter: experts say two accidents in which human failure was at least partly to blame underscore that remains the biggest threat to safety. air france 447 crashed into the atlantic in 2009, killing 228.