Curiously there has been no mention in this thread of the want of a third, fail safe spar in the horizonal stabiliser on the B707 in the design office - might have saved them - never know. A great read is, J M Ramsden, "Caring for the Mature Jet", released after the Lusaka accident. I learnt and absorbed all my basic mechanical flight control basics on the B707 that still hold true today . . . I got lucky and went on to the B727-200ADV for a few years after that and never looked back !