By Jeff Pardo

At 11:09 a.m. on Sunday, December 1, 1974, a Boeing 727 operating as TWA Flight 514 was in IMC and inbound to the Washington Dulles International Airport. Due to an ambiguous approach procedure and a misunderstood clearance, the crew descended prematurely to their final approach altitude, which in fact wound up being their final altitude; they collided with the western slope of Mount Weather in Berryville, Va. All seven crewmembers and 85 passengers were killed.

Six weeks earlier, a United Airlines flight had narrowly avoided the same fate during a nighttime approach, discovered their close call after landing, and promptly reported it to United’s new Flight Safety Awareness Program. A notice…