In the late 1960s, a series of controlled flight into terrain (CFIT) accidents took the lives of hundreds of people.
A CFIT accident is one where a properly functioning airplane under the control of a .
fully qualified and certified crew is flown into terrain, water or obstacles with no apparent awareness on the part of the crew.[3]
Beginning in the early 1970s, a number of studies examined the occurrence of CFIT accidents.
Findings from these studies indicated that many such accidents could have been avoided if a warning device called a ground proximity warning system (GPWS) had been used.
As a result of these studies and recommendations from the U.S.
National Transportation Safety Board (NTSB),
in 1974 the FAA required all large turbine and turbojet airplanes to install TSO-approved GPWS equipment.
