Cheers to Yellow Sun for that very helpful explanation!
BB - Is there anything more you can remember about the incident that might be of interest? For instance, was anyone injured, and/or did they have to be cut out of the a/c or were able to exit normally? I don't suppose you can remember their names? If it helps jog your memory, it would have been one of the following: Assefa Mekbib, Bizuwork Yigezu, Afeworki Mekonnen or Mesfin Haile. I've interviewed the latter two, and neither mentioned it, so I am guessing it was one of the former. I know we are talking 51 years ago, but hey, it's worth a shot!
One other thing - what was Viv's full name - and is he 'available for comment' so to speak?