A British girl (Victoria Shaw) broadcasting for the Germans as a double agent obtains codes and frequencies for the Allies.

A dishonorably discharged flier (James Franciscus) masquerades as a replacement pilot in order to fly one combat mission.

When Gallagher and a pilot who resents him are shot down over the North Sea, they're rescued and treated with surprising decency by a U-Boat commander -- but the Nazi turns out to have a sinister hidden motive.

Fighter pilot Harley Wilson wants to be accepted by his fellow airmen, but sometimes he tries too hard—-as when he accidentally shoots up Gallagher's B-17 while trying to down a German plane. 

On the way back from a bombing run over the Ruhr Valley, Gallagher's battle-damaged B-17 accidentally drops its bombs on Ste. Monique, France. 1st Lieutenant Parks, the bombardier, is interrogated. A single bomb falls in the village square, killing resistance leader Pierre Fecamp. Two American pilots hiding in Ste. Monique escape: Major Coefield from the 918th and Captain Pollard from the 511th Fighter Squadron. Pollard has fallen in love with Claudine, the woman who rescued them and the daughter of Fecamp. She has brought her son to England badly wounded from the bomb's explosion, and he may lose his leg. Claudine hates Gallagher and is going to kill him. She goes with him to the 918th Officers Club and sees the pilots get drunk. Meanwhile, in Ste. Monique, Hauptman Bergdorf says they will not bomb again because of the last mission, so now they can put in a German Radar Station. On the way to Wing HQ in Archbury, Claudine tries to kill Gallagher. General Marteen orders the 918th to bomb Ste. Monique that night. In Ste Monique, German soldiers kill Marcel Lenoir as he radios information to London.

Off the base, JayDee Jones is working up the nerve to go on his next mission. He gets Jan Warner to sneak him back on base. He gets spotted by Chapman who is stealing 3 45 pistols to sell. JayDee's older brother Frank talks to him and tells him to straighten up. JayDee says he has had enough, he wants out. Jones and Chapman make briefing at 04:30. On takeoff JayDee over-revs his B-17's engines, but they don't have enough speed to take off. His co-pilot tries to help but the plane crashes killing the bombardier and badly injuring the co-pilot who dies later. Frank covers for his brother and says it could be a maintenance problem. Colonel Hunter the Wing G-4 (Supply) comes to investigate. Chapman sells his pistols to an Englishman who gets caught. Captain Mason from CIC comes to investigate the stolen guns. Jones co-pilot dies. Chapman and JD talk, Chapman says him will back Jones up. Hunter and Gallagher interrogate JayDee Jones, Frank Jones and Chapman. Chapman backs Jones who still can not remember

The 918th is being chewed to pieces while attempting to bomb a target in Norway, so secret that even Joe Gallagher doesn't know what it is or why it's so important. In fact, in its latest try, the mission commander, Col. Christie, decides to abort and turn back only 4 minutes from the target after losing 8 out of 21 bombers, with 4 more heavily damaged, including his own. Infuriated by the excessive losses and secrecy surrounding the missions, Joe alienates his superiors when he aggressively defends Christie against a looming court martial. To the rescue, possibly, rides his father, Lt. General Gallagher, who is hellbent on getting his son his first general's star. But Joe is in no mood to discuss promotion with his friend and the reputation of the 918th teetering on the edge of oblivion.

The 918 is on its 8th mission to bomb the submarine pens at St Nazaire. Major Kurt Brown, who leads this mission, has never aborted for any reason. Richards, Brown's bombardier, is badly wounded, and Brown tells his Navigator to hold him to the bomb sight. He completes his mission but is annoyed at the cost and argues with Colonel Gallagher. On eight missions, they have lost 34 aircraft. Later in the Star & Bottle, Gallagher asks Brown to drive Elizabeth Hoffman home. On his next mission (43rd), he aborts because his Navigator has appendicitis. Elizabeth tells Brown she is German. Brown is angry. He flies his 44th mission and is in a daze. Brown finally admits that he loves Elizabeth. Before the next mission, Brown passes out from exhaustion before flying.

On a practice for a night mission, Lt. Fay Vendry's unit tracks Col. Gallagher's B-17. They change course and evade successfully, but Capt. 'Chub' Willis has to correct, as he was off target. Chub is distracted by his girl, Kitty. On the actual night mission into Norway to pick up legendary resistance leader Arn Borg, they are told to look for the King Frederick light. It appears to be a trap as the Germans are waiting. The plane gets shot at, lands, and picks up Borg, who brings his son Christian back with him. Gallagher is angry. Back at base, Borg's map is impossible to read. Gallagher is ordered to fly another reconnaissance mission. Borg runs away, so they decide to take Christian to show them the target. Borg comes back and flies the mission. They bomb what seems to be a heavy water storage facility, and the mission is successful. Borg returns to Norway.

On a mission, 9 out of the 10 crew of the Piccadilly Lily are wounded, save one - Komansky. Komansky flies and lands the plane, becoming a press celebrity. A wounded Gallagher puts him in for the Silver Star. Kirby Wyatt, the 918th press liaison, calls Susan Nesbitt, an American correspondent working for the BBC. She takes advantage of Komansky, realizing this story could make her (he rescued General Gallagher's son). Kirby Wyatt goes along with Susan. Sandy is very uncomfortable with the celebrity. He is kidded about being a jinx by Technical Sergeant Chapman, Major Benson's Flight Engineer. Sandy replaces him on a mission and has to kick a bomb loose. Sandy is awarded the Silver Star.

The 511th Fighter Group with new P-51s arrives at Archbury to escort the 918 on the home leg of the shuttle mission. On the way, Lieutenant Col. Troper attacks a train, making him 10 minutes late for the rendezvous. The 511th fails to provide the proper recognition codes, and Gallagher's B-17 accidentally shoots down one pilot. On the ground, an angry Troper slugs Gallagher. Gallagher tells Troper to forget about it. They are ordered to train together. In London, Troper gets drunk, insults Gallagher, and takes off with Gallagher's date, Lt. Fay Vendry. Gallagher orders a mission briefing at 0400, but only 12 of the 511th pilots show up. Gallagher has Troper put under house arrest. Merritt leads the fighters, and no bomber is lost.