Capt. Marvin Renslow had never been properly trained by the company to respond to a warning system designed to prevent the plane from going into a stall, according to people familiar with the investigation. As the speed slowed to a dangerous level, setting off the stall-prevention system, he did the opposite of the proper procedure, which led to the crash, these people said.

Additionally, his 24-year-old co-pilot, Rebecca Shaw, had complained before takeoff about being congested and said she probably should have called in sick, according to people who have listened to the cockpit voice recording.