A Yank in the R.A.F.

In 1940, North American Harvard training aircraft are flown to the US-Canada border and towed across to Britain, complying with the Neutrality Acts. The process is necessary to supply Britain with aircraft while maintaining US neutrality during the early stages of WWII.

American pilot Tim Baker secretly flies across the Canadian border to Trenton, Ontario, and gets into trouble with the military authorities. He claims he was searching for Trenton, New Jersey, but his true intent was unauthorized flying to Britain.

Baker is advised to ferry Lockheed Hudson bombers to Britain, earning $1,000 per trip. This assignment marks his initial involvement in wartime aircraft delivery efforts for Britain.

Baker reunites with his girlfriend Carol Brown in London, where she works in the Women's Auxiliary Air Force and performs in a nightclub. Their reunion is tense, as Carol is upset with his womanizing and long absences.

Deciding to serve officially, Baker enlists in the Royal Air Force. Simultaneously, Carol attracts attention from RAF officers, Wing Commander Morley and Flying Officer Pillby, creating interpersonal tension.

After completing his training, Baker is assigned to Morley's bomber squadron and is disappointed not to be in a fighter unit. His first mission involves dropping propaganda leaflets over Berlin during the Phoney War.

Baker misses a date with Carol due to meeting an old friend, leading her to accept an invitation from Morley. Morley proposes marriage, prompting Baker to casually offer to marry her himself, causing a breakup between Carol and Baker.

As Germany invades the Netherlands and Belgium, Baker flies a mission to bomb Dortmund. Their bomber is hit, with one engine disabled, and Pillby sacrifices himself to clear searchlights before being shot down, leading to Baker and Morley's capture.

Baker and Morley hide in a building on a Dutch beach after their plane is shot down, then escape by motorboat, narrowly avoiding German soldiers and rescuing a crewman who sacrifices himself during the encounter.

Baker wakes up in a British hospital suffering from exposure, then visits Carol Brown, pretending to have a broken arm. He shows her a ring but is revealed to be dishonest about his feelings. Their relationship remains strained.

Baker is called up as a fighter pilot for the Battle of Dunkirk, flying a Spitfire. He successfully downed two Luftwaffe fighters before being shot down himself, marking his active combat role in the war.

After the Dunkirk evacuation, Carol fears for Baker's safety. She finds him returning from the beaches, still wearing his engagement ring, symbolizing their ongoing connection despite the dangers of war.