No apologies needed! I was unsure why the question was being asked. I had no idea what the actual Mach crit for the 747 was, but I do know that noticeable separation takes place and high speed buffet sets in on these type jets at about M.93, and Rainboe doesn't like that sort of thing! I guess some people make born test pilots and some don't. I'm on the 'don't' side!