became a nuisance warning because they had heard it intermittently before. they didn t know if it was valid or not and decided to disregard it. we ll never know. they never discussed it. reporter: the initial french investigative report states that a phenomenon called the startle effect may have played a role. it is similar to walking in to a room that s dark and somebody jumping out and saying boo. it s that instantaneous scare, if you will. the auto pilot is off. why is it off? what do i need to do? and now you are having to process this information in a compressed time line. human beings when they are focused on one task, thing s will drop out. oral inputs of are one of the first to go. so this is consistent with this pilot not hearing, therefore not responding. reporter: prior to the crash of flight 447, airbus and air france had recognized the
controller, you may not notice the slight motion, doesn t take a lot. it is possible that you can have a full aft stick input and the other crew members don t notice it. the airplane is only seconds from hitting the ocean. the passengers really probably didn t understand what the gravity of the situation was. they only knew possibly that they were entering an area of turbulence. air france 447 smashes down belly first into the atlantic killing everyone on board. autopsies of the victims reveal compression fractures of the spinal column and pelvis. injuries combatble with a seated person hitting the surface of the water at high vertical speeds. it s still unclear whether pilots did not recognize that the plane had stalled. despite the useable stall warning that sounded for 54 seconds. it may have been that it became a nuisance warning