Playing devil's advocate here, and trying to see it as Joe Public sees it when all goes to plan. At the end of the parade when the royal party are up on the balcony what happens? A few very small formations of sundry aircraft come stooging down The Mall at a safe but not very exciting height. First you get a big one with a couple of little ones. Then maybe two big ones and two little ones. Then a few helicopters. Then maybe four little ones all the same shape and size. Oh and the BBMF (but for how much longer?).
Then you get the Red Arrows streaming red, white and blue smoke.
I'm guessing that this is the only bit of the flypast that really impresses anyone, unless they have a particular interest in military aviation. Frankly I doubt if many in the crowd today missed the cancelled aircraft, as at least they got to see the Reds. Is it all worth the three months of planning and coordination that handleturning describes?
Just sayin'!
Incidentally social media (twitter etc) is alive with chat about the Duchess of Cambridge's hat - obviously of much greater interest than the lack of a flypast!