IncidentThe Foo Fighters (1944–1945)

Allied pilots over Europe and the Pacific reported luminous spheres pacing their aircraft, fast, silent, and unresponsive to evasive maneuvers.

A B-17 of the 8th AAF over Europe in late 1944 — the same theatre and months in which the 415th Night Fighter Squadron logged the first 'foo fighter' reports.Wikipedia Commons · Public domain · Unknown authorUnknown author or not provided · 1943

What's documented

The term entered Allied pilot vocabulary via the 415th Night Fighter Squadron flying P-61 Black Widows out of Dijon and Échallens in late 1944. Reports described balls of orange-red light, 1–5 feet across, that would form on or near the aircraft, follow for minutes, then accelerate away. The Robertson Panel of 1953 reviewed the wartime files and declined to attribute a cause.

Notable & intriguing

Lt. Edward Schlueter of the 415th Night Fighter Squadron reported the first formally logged encounter on 14 December 1944 over the Rhine, accompanied by intelligence officer Lt. Fred Ringwald.

415th NFS squadron logs; Time magazine, 15 January 1945, p. 28
The Eighth Air Force's 415th NFS flew 119 combat missions out of Échallens and Ochey in the winter of 1944–45; foo-fighter reports appeared in roughly a dozen of the after-action mission summaries.

415th NFS after-action reports, USAF Historical Research Agency
The phenomenon was reported simultaneously by USAAF crews over Germany and by B-29 crews over Japan in the same months; no Axis weapons program is known to have produced anything matching the descriptions on either front.

Project Sign Report, 1949; declassified USAF microfilm