Night Plane from Chungking

Night Plane from Chungking aka China Pass and Sky Over China is a 1943 American war film released by Paramount Pictures, directed by Ralph Murphy, and produced by Michael Kraike and Walter MacEwen from a screenplay by Lester Cole, Earl Fenton and Theodore Reeves, adapted by Sidney Biddell from the story by Harry Hervey. The film stars Robert Preston and Ellen Drew, with Otto Kruger and Stephen Geray.

Another of the passengers, Doctor Van der Linden Stephen Geray, goes missing, but returns with food he claims comes from a nearby monastery. The doctor leads everyone on a long hike to the monastery, only to reveal there that he is a Nazi collaborator working with the Japanese. He demands to know where Olga is, not knowing she is dead. All the survivors are captured and held at the monastery.It is up to Nick to try to come up with a plan to escape, and convinces Van Der Linden to allow Po to repair the aircraft and to allow the hostages to be exchanged for Olga. A coded message is sent to Nicks headquarters but the Nazi soon finds out that Olga is already dead. After Pasavy betrays the others, and is coldly shot, Nick kills Van der Linden. With Japanese troops in pursuit, Major Raoul Brissac Ernest Dorian sacrifices his own life to save the others by pulling the pin on a grenade, killing himself along with the Japanese. Nick, Po, Ann and Madame Wu then fly to safety. Having fallen in love, Nick and Ann vow to reunite after the war. ........

Source: Wikipedia