 However, the accident aircraft had developed a cracked rear right spar without the fault being detected due to its location within part of the structure not normally accessible during routine maintenance, and the aircraft had been flown for a considerable number of hours with the fault present.Over time the crack grew, until it was surmised, the damaged spar was no longer capable of carrying its designed load, whereupon the load was then taken over entirely by the front spar.The accident aircraft encountered several strong gusts during the approach immediately before the accident which, while not dangerous to a structurally sound Boeing 707, exceeded the load capable of being carried by the remaining intact spar on its own, leading to the spar eventually breaking and resulting in complete structural failure of the entire right horizontal stabiliser.