I was just talking to a friend that took the DL BizElite 767-300ER service from JFK to SFO yesterday.
He said the weather was exceedingly bad, and that they cruised around FL430 a good part of the trip.
I was under the impression that the 763's max alt was only FL410.
This prompted a discussion of altimeters. We visited the possibility that the turbulent air caused a misread with a barometric altimeter. But then he pointed out that a lot of planes judge alt via GPS now.
Can anyone shed some light?