Guthrie's tenure at BOAC was marred by a two fatal incidents; the first, BOAC Flight 911, occurred in March 1966 when a Boeing 707 experienced clear-air turbulence whilst overflying Mount Fuji in Japan. The crash resulted in the deaths of all 124 passengers and crew, the most deadly accident involving a British airline to date. Guthrie travelled to Japan to be involved in the investigation. The second fatal accident, BOAC Flight 712, also involved a Boeing 707. The aircraft suffered an un-contained engine failure during takeoff; returning to Heathrow, the engine separated from the wing, causing the wing to catch fire. The aircraft cabin was destroyed by fire, and five people were killed.