Air Traffic Control & Pilot Communication Errors – Disambiguation, Context & Redundancy

On February 19, 1989, a Boeing 747-249F operating as Flying Tiger Flight 66 was flying an international cargo flight from Singapore to Kuala Lumpur, Malaysia… ATC radioed to the flight, “Tiger 66, descend TWO four zero zero [2,400 ft]. Cleared for NDB approach runway three three”. The captain of Tiger 66, who heard “descend TO four zero zero” replied with “Okay, four zero zero” (meaning 400 ft above sea level, which was 2,000 ft too low)… the aircraft impacted a hillside 437ft above sea level, killing all four people on board; two pilots, a flight engineer and an aircraft mechanic. The subsequent fire burned for two days…

http://en.wikipedia.org/wiki/Flying_Tiger_Line_Flight_66
See “Rorschach Audio” book pages 21, 115, 116, 130 and 151