Some direct link context on ground proximity warning system (GPWS) https://en.m.wikipedia.org/wiki/Ground_proximity_warning_system#History https://en.m.wikiped

Some direct link context on ground proximity warning system (GPWS) https://en.m.wikipedia.org/wiki/Ground_proximity_warning_system#History https://en.m.wikipedia.org/wiki/Ground_proximity_warning_sys... https://en.m.wikipedia.org/wiki/Terrain_awareness_and_warning_system#History https://en.m.wikipedia.org/wiki/Terrain_awareness_and_warnin... Or, to provide an excerpt: >> "Prior to the development of GPWS, large passenger aircraft were involved in 3.5 fatal [controlled flight into terrain] accidents per year, falling to 2 per year in the mid-1970s. A 2006 report stated that from 1974, when the U.S. FAA made it a requirement for large aircraft to carry such equipment, until the time of the report, there had not been a single passenger fatality in a [controlled flight into terrain] crash by a large jet in U.S. airspace." Preventing 2 aircraft accidents per year is a very impressive legacy. >> Note: "After 1974, there were still some CFIT accidents that GPWS was unable to help prevent, due to the "blind spot" of those early GPWS systems. More advanced systems were developed." (i.e. flying into a vertical feature that a down-looking radar altimeter can't see)