No Highway (in the Sky) (1951)

The above are both the British and the US titles for this odd concoction.  It's been a long time since I last saw it, but my theory is that any film with James Stewart in the lead can't be all bad -- and you know what, he makes this story watchable.  He's in his absent-minded professor mode here as an aeronautics engineer convinced that the tail will fall off certain airplanes because of metal fatigue after a specified number of flying hours -- and nobody believes him, until he finds himself aloft with stewardess Glynis Johns and sexy screen siren Marlene Dietrich.  He's surrounded by a slew of British character actors of the period who are irrelevant, as are the female leads to some extent; he's the whole show and you gotta love him in his persistence.