Excerpting from the post by Cornish and focusing on one element.
20 separate people do not miss the fundamental safety checks on seats....
Back when I learnt about seats as a humble liney I, like everybody else was taught that you are climbing on a bomb, one that wants to fire, one that wants to kill you and will do so if you do not give it 100% respect for every single second you are working near it.
Looking back a zillion years ago to my days as a humble liney on Vulcans, Hunters and Frightnings I have to identify with the suggestion that "20 separate people" is a sufficiently large number to swallow. Granted there are differences in seat type, installation and generation (seats and people) but the fundamentals in training and awareness of hazards I feel pretty sure are still there, or certainly should be. Over the time I was active in line and ejection seat work I encountered a few hairy "there but for the grace of God" type personal lapses that are the inevitable consequence of requiring a human interface and such are always present but, it's the "20 separate people" bit that I find hard to swallow and should be a worrying number. Heavens above, one would have thought that at least one of those 20 would have identified that something was not quite right; another element in the mounting sequence of events perhaps ?