 C. Donald Bateman, an engineer at Honeywell, is credited with developing the first ground proximity warning system (GPWS); in an early test, conducted after the 1971 crash of Alaska Airlines Flight 1866, the device provided sufficient warning for a small plane to avoid the terrain, but not enough for the larger Boeing 727 jetliner involved.Bateman's earliest devices, developed in the 1960s, used radio waves to measure altitude and triggered an alarm when the aircraft was too low, but it was not aimed forward and could not provide sufficient warning of steeply rising terrain ahead.Findings from these early studies indicated that many such accidents could have been avoided if a GPWS had been used.