A French fighter jet carrying two pilots has disappeared from radar screens near the Swiss border.
A French air force spokeswoman said the Mirage 2000D was last detected in a snow-covered mountainous area between the Doubs and Jura regions.
She said a search is under way for signs of the plane.
The jet took off shortly after 11am local time from the Nancy-Ochey air base in north-east France.
The pilots had been on a low-altitude training flight.
Mountain rescuers, firefighters, police, military units and local residents joined the search effort, according to the regional administrations of Doubs and Jura.
Visibility was extremely low, with heavy fog and snow.