Not a height record but a story that may bring a smile.
Back in the 70s going down to Offutt from the Goose in the Avro Galactic Starship we were cruising at FL370 using UHF when we heard the controller's side of a VHF conversation:
"That's a British Air Force Vulcan sir"
pause
"He's at FL370"
pause
"Roger, N1234 you're cleared to FL390"
So we asked for and got FL410
pause
"Roger, N1234 you're cleared to FL430"
We asked for and got FL450
long pause
"RAFAIR 123, the Learjet says OK, you win!"
