British and French naval and aircraft forces clashed according to the U.S. Joint Intelligence Committee. Daily summary dated 20 May 1942

An item reported that around noon 18 May French and British naval and aircraft forces clashed. French aircraft fired on a British Catalina flying boat patrolling off Algiers and which was forced to land on sea about 15 miles off Cap Caxune. A British cruiser and a destroyers arrived to assist her fired at two French destroyers, the latter claiming that they also want to assist the Catalina crew. In a fight between French and British aircraft each side lost one plane.

Source

Map Room Papers (Roosevelt Administration), 1942 - 1945. U.S. Joint Intelligence Committee. Daily summary No. 161 dated 20 May 1942