Michel Tanguy and Ernest Laverdue are sent to the Dijon airbase. When they arrive they end up half naked in front of the commanding officer. They also attract the attention of a mysterious Mr X who makes Tanguy a proposal.

The head of the airbase receives a copy of a gambling debt signed by Tanguy. He may therefore be dismissed from the air force. Meanwhile there are problems with the oxygen supplies at high altitude.

Two Canadian officers, Lester and Gagnon arrive at Dijon to fly the Mirage, but they are intercepted and replaced at the airport the journey by two lookalikes.

The Canadian officers are suspected as replacements by the captain, but is unable to raise the alarm.

The captain has an accident caused by the spies who have infiltrated the base.

A young pilot, Larrafieu joins the squadron. He is afraid due to having had an accident that killed his wingman. The commander tries to get him to resign.

Tanguy tries to complete a mission instead of Larrafieu in bad weather. Together with Laverdue he helps Larrafieu regain his confidence.

Laverdure has dinner with Nicole. Tanguy has to stay at the base. Meanwhile Mr X sends a spy plane to photograph the new French nuclear facility.