A final report from the UK Air Accidents Investigation Branch (AAIB) said a missing rivet head on a fuel shutoff valve that likely led to inadvertent engine shutdown was one of four “contributory factors” that resulted in the crash of a Cessna Citation 500 on March 8 some two miles northeast of London Biggin Hill Airport. Shortly after takeoff from Biggin Hill, the crew radioed they were returning immediately, reporting “engine vibration” and, subsequently, “a major power problem” before the 1975-built, Bermudan-registered twinjet hit a house. The two crewmembers and three passengers on board died in the accident; no one on the ground was injured. Other contributing factors included an air-cycle machine mechanical failure that likely caused the vibration reported by the crew; the fact that neither engine was producing thrust shortly before impact; and an attempted relighting of the second engine that likely began before the relit first engine had reached idle speed. The AAIB issued several recommendations as a result of its findings. It is asking the International Civil Aviation Organization (ICAO) to require flight-data recorders on turbine aircraft with an mtow of less than 5,700 kg (12,566 pounds). Two recommendations were sent to the FAA: require Citation 500 throttle-quadrant assembly inspections to ensure fuel shut-off levers are securely attached to throttle levers; and amend emergency checklists for the Citation 500 to emphasize that engines should be restarted individually.