Some years ago - I think 1984 but couldn't swear to it - I was at an airshow where a couple of Luftwaffe Starfighters flew over the crowd at RAF Fairford at slightly over M 1.0 Apart from a very loud bang, the only noticable effect was to make every kid cry and to set every car alarm off.
Neville Duke regularly put his Hawker Hunter though M1.0 during the SBAC airshows at Farnborough in the 50s but I'm too young to have seen that.
--Mik
[ 28 August 2001: Message edited by: PPRuNe Dispatcher ]