On 7 March 1977, a Mirage IV crew near Chaumont reported being pursued by an unidentified object.

The Mirage IV pursuit matters because it is a French military case.
Documented
A Mirage IV crew reported an unidentified object
Debated
The identity of the object
Unverified
Extraterrestrial origin
Sources are kept in separate layers: official and contemporary material is documented; secondary UFO literature is treated as debated, not as primary evidence.
Documented source.