Greg 'groggy' Lehey writes:
Another hypothesis I had ties in with this: both he and Bill Gates
were speakers at Euromicro 1980 in London, from 16 to 18 September.
Bill Gates was a no-show. Would that fit in with Gary's "gone
flying"?
Greg
According to Tom, no, he was visiting a somewhat local customer, I
think in the bay area, which is why he was flying his plane. This
wasn't the modern times when CEOs owned fancy jets.