For a B film Crack-Up has a more complex plot than usual and some of the characters are clearly modeled on some prominent figures, Brian Donlevy is Floyd Bennett and Ralph Morgan to me represents Orville Wright.
But Peter Lorre steals this film in a turnabout performance. When we first meet him he's a local character who hangs around an airfield who no one quite takes seriously. Than later we learn he's actually the head of a spy ring for an unknown country, but I'm thinking the Soviet Union.
Donlevy is not only an ace pilot, but an aircraft designer and he's got a new type model propeller that Lorre's crowd wants. Circumstances and the film's plot bring Morgan, Donlevy, and Lorre together on a downed plane which Donlevy was piloting on an experimental New York to Berlin run. The dynamics between these three and young Thomas Beck on the plane to Berlin is quite interesting.
This one is a neglected sleeper. Try to catch it.