Graveyard of Dreams by H. Beam Piper — Read

Standing at the armor-glass front of the observation deck and watching the mountains rise and grow on the horizon, Conn Maxwell gripped the metal hand-rail with painful intensity, as though trying to hold back the airship by force. Thirty minutes -- twenty-six and a fraction of the Terran minutes he had become accustomed to -- until he'd have to face it.

Then, realizing that he never, in his own thoughts, addressed himself as "sir," he turned.