The Gulfstream GIV was on a repositioning flight from Nice, about 100 miles away, to Le Castellet near Toulon, AINonline reported. It was carrying no passengers, witnesses said.
The victims' names were not released. Officials said all were U.S. pilots and included two men, aged 61 and 24, and a woman, 30.
Witnesses told local news media the plane broke up with one section catching fire and the other plunging into a lake near the runway.
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