The WWII "Foo Fighters" (1944)
Starting in November 1944, Allied night fighter pilots of the 415th Night Fighter Squadron, flying over the Rhine Valley near Strasbourg, reported being chased by small balls of orange, red, or green light, capable of outmaneuvering their aircraft and never appearing on radar. The phenomenon, nicknamed "Foo Fighters," recurred across both the European and Pacific theaters of operations.
Witnesses
Allied fighter pilots
Why it endures
Hundreds of experienced military pilots, on both sides of the conflict, reported an identical phenomenon that was never explained as an enemy secret weapon.
Official version (contested)
Explanations proposed at the time include flares, weather balloons, or St. Elmo's fire; none was ever confirmed with certainty.