Chasing 4 Jags up the Great Glen at 250-ish (honest, Ossifer) a certain pilot of my acquaintance noticed 'transonic jump' on the altimeter of his F4 and saw Mach 1+ on the ASI/machmeter......
Went past the Jags (1 x Fox 2 each) at the speed of heat. Hope Mrs Osprey's eggs survived the fun..........err, he said!