Pilots risk their lives flying mail over the Andes, and a woman visitor explores whether love with such is possible.
At the port of Barranca Les Peters (Allyn Joslyn) and Joe Souther (Noah Beery Jr.) follow Bonnie Lee (Jean Arthur), who joins her fellow countrymen for a drink. Geoff Carter (Cary Grant) tells Joe he must fly the mail. Because of fog, Geoff calls Joe back, and he crashes. Geoff blames Bonnie, because Joe tried to land to see her. Bonnie gets upset they don't mourn; but she understands and plays hot piano. Geoff stays up with Bonnie and says he wouldn't ask any woman. Kid Dabb (Thomas Mitchell) says it is dangerous, and Geoff goes up. He comes back to find Bonnie did not sail. Dutchy (Sig Ruman) brings new pilot Bat MacPherson (Richard Barthelmess). Les says he once bailed out and let Kid's brother die, and Geoff warns MacPherson. Kid recognizes him, and MacPherson introduces his wife Judith (Rita Hayworth).
Geoff sends MacPherson with a doctor to a tight spot. Geoff tests Kid's eyes. They need one more week of carrying mail to earn a subsidy for Dutchy. Geoff tells Kid he can't fly anymore. MacPherson flies, lands, and makes it out. Judith and Geoff know each other, and she did not tell MacPherson. Geoff stops Kid from choking Gent Shelton (John Carroll), and Les says his arm is broken; but Kid apologizes. MacPherson lands, and Geoff tells him he has a job. Geoff gives Dutchy the large check and tells him to give MacPherson a good room. Geoff tests a plane and barely lands; Bonnie gets upset, and Kid consoles her.
Gent refuses to fly nitroglycerin; Geoff gives the map to MacPherson. Judith asks why he gets these jobs. Geoff radios MacPherson to come back and drop the nitro on the condors. Geoff tells Judith to ask her husband. Geoff sees her tipsy and pours water on her head. Geoff finds Bonnie in his bath and making coffee. Judith comes in, and Geoff says she can radio MacPherson. Geoff kisses Bonnie, and she says she won't ask him to change. Kid comes in and wants to go on the test flight too. Dutchy tells Geoff not to go in the storm. Bonnie tells Geoff she is packing to go but takes his gun. She drops it, and it wounds him in the shoulder. MacPherson brings the mail and goes with Kid. They climb to 15,600 feet and then dive. Kid radios they are going through the pass even though Geoff says no. A condor breaks a window, knocking out Kid. An engine is on fire. MacPherson refuses to bail out. They crash land and are pulled out. Geoff tells Kid his neck is broken, and Kid tells him to buy MacPherson a drink. Dutchy says the field is closed down. Sparks (Victor Kilian) tells Bonnie to say good-bye to Geoff. She sees he is crying over Kid's death. Tex radios that the pass is clear. Geoff goes up with Les, and Bonnie realizes that he wants her to stay.
This tough drama foreshadows the dangers of the coming air war as men and women learn how to be detached about life and death.