A tragic mistake of war took place on July 8, 1944 when Swordfish aircraft from two MAC ships (Merchant Aircraft Carrier) attacked and sank the Free French Navy submarine La Perle off Newfoundland. The submarine was seen running on the surface by one of the aircraft which was on a routine patrol, after the pilot reported the sighting several more aircraft were launched to make the attack.

Even though the submarine flashed the correct identification signal, this was ignored by the aircraft. Those back on the ships had been informed that the French boat was in the area, but for unknown reasons failed to react to the situation before it was to late. La Perle went to the bottom with all but one of her crew, CPO Machinist Emile Cloarec.