Of the many never explained observations of unidentified flying objects reported in the twentieth century, the tales of strange, glowing balls of light maneuvering around warplanes over Europe and the Pacific during the Second World War still remain a mystery. When first encountered by Allied fliers, they assumed it was some new type of weapon thrown at them by the Axis war machine despite there being no incidence of one of these objects acting in a hostile manner. Conversely, when the Axis pilots encountered what was to become popularly known as "foo fighters" they too believed them to be machinations of the enemy. To date, no one knows what they were or where they originated.

Foo fighters pacing a formation of B-17 Bombers over Germany
The first reported sightings began in November of 1944 by Allied airmen during nighttime bombing runs against German factories. Radar operator Donald Meiers of the 415th Night Fighter Squadron gave them the name based on the phrase, "where there's foo, there's fire" in the Bill Holman cartoon strip "Smokey Stover" because the objects first appeared to them as glowing red balls. The objects chased the Allied aircraft and easily followed through a series of high-speed maneuvers.
As the sightings increased, more pilots and airmen described the strange objects as fiery, glowing red, white, or orange. They were disturbed by the lights which they said were "toying" with them. The foo fighters could perform "wild turns before simply vanishing." Often the objects would fly in formation with the Allied bombers and acted and reacted as though intelligently controlled. While never offering hostile behavior, all attempts to force the craft were met with failure as they easily outmaneuvered pursuing fighter planes.

Foo fighters approaching a Japanese torpedo/bomber
Reports of foo fighters quickly began coming in from the Pacific Theater of Operations as well. There were, however, some differences in the look and behavior of some of the unidentified flying objects spotted there. The "ball of fire" appeared more like a glowing, burning sphere and was often seen hovering although they occasionally followed the aircraft. This led to one reported incident where the gunner of a B-29 bomber fired upon a foo fighter that got too close to his aircraft. He reported that he managed to hit the craft that then broke into several pieces that fell to the ground. Being over enemy territory, there was no way to go back and investigate the wreckage.
Scientists and debunkers have tried to explain away the airmens' sightings in a variety of ways. Some claim that the swift moving objects were just electrostatic discharge, "St. Elmo's Fire," without taking into consideration that these experienced fliers were familiar with the electrical phenomena and would have recognized it for what it was were that the case. Some went so far as to say it was just light reflecting off ice crystals. Another ground-based theory was that the airmen were merely seeing the afterimage of flak bursts despite there having been anti-aircraft fire hurled at them long before the winter of 1944.

Foo fighter playing with a Concorde over the UK. Date thought to be somewhere between the late 1970's to early 1990's.
Even after the War was over, the glowing fireballs known as foo fighters would make occasional appearances chasing after aircraft like dogs after cars. Even when the more recognizably constructed "flying saucer" caught the public imagination and the flying cigars left observers knowing they were seeing a flying machine, the glowing spheres would still turn up and remind us that the mystery of the foo fighter has never been solved.