Hunter Avpin starters.
I was at a Chivenor airshow about 1972. There was a lull in the flying so I was walking near a line of 40 Hunters that had some activity around them. Suddenly all 40 started at the same time. I nearly fouled my breeches with the noise.
They did some aerobatics in "229" (OCU) formation using 36 aircraft.
I think it was the same year that 229 OCU did the same thing at Farnborough in "E II R" formation.