Air mail pilots risk their lives to carry Christmas mail in this action classic directed by John Ford.
In the fog Joe Barnes crashes and burns on the airfield. Mike Miller (Ralph Bellamy) consoles his sister Ruth Barnes (Gloria Stuart). After a loss supervisor Mike always flies the next run. A doctor tells him to stop flying because of his eyesight and says he will lose his passenger license. Mike dislikes the new pilot Duke Talbot (Pat O'Brien), who buzzes the airport and does air acrobatics. Mike tells Duke not to show off and takes away his alcohol. Duke shows his medals and plans to return to the Balkans. Dizzy Wilkins (Russell Hopton) quarrels with his wife Irene (Lilian Bond) and takes off in a storm during the Christmas rush. Duke comes in to see Irene and says he doesn't know the difference between good and bad. Ruth asks Mike to be Santa Claus. Mike asks Irene if she wants a Christmas tree, and she tells Duke to leave, fearing Dizzy would kill her.
Duke lands during a snow storm when passenger flights are grounded. Dizzy calls in flying low. A passenger plane is forced to land there. Tony is identified as Larry Thomas, the only pilot to parachute and leave his passengers to die. Duke kisses Irene. Dizzy's plane hits a power line and crashes. Mike and Slim (Slim Summerville) go out in a truck and find Dizzy as he dies. Mike brings back the mail bags. Ruth tells Mike not to go, because she loves him. Slim tells Mike to let Duke take it because of his eyes. Tony asks Mike to let him go so that he can redeem himself. Mike decides to ask Duke; but he is packing his bags and quits; they quarrel, and Mike slugs him. Mike takes off in the snow storm. Duke and Irene leave with the passengers on the bus. Duke reads news reports that Mike is missing. Planes search the snowy mountains. Duke and Irene drink a toast and hear on the radio that Mike was found in an inaccessible place. Mike signals pilots not to land. Supplies are dropped, but Mike cannot move because of a broken leg. Duke leaves Irene to save Mike. He takes off and lands near Mike. They manage to take off, knocking off the wheels. The plane is falling apart, and Duke did not bring a parachute. He flies upside down to dump Mike out and then crashes. In the final scene Duke is in an ambulance with Mike and Ruth. Nothing stops the mail.
Brave pilots take stunning risks in the early years of air mail. Wives and girlfriends suffer losses and worry too. The cocky Duke emerges as more heroic than selfish in saving the courageous Mike. Great sacrifices are made so that people can send letters faster.