More information about the Foo-Fighters here.
NEWSWEEK - Jan. 15, 1945
That was more than a month ago, one of the first times Allied fighters encountered what they now call "foo-fighters."[*] In addition to the wingtip balls, pilots have reported two other types (1). One is a group of three smaller balls which fly in front of their planes, the other a group of about fifteen which appear some distance away and flicker on and off (2). Apparently controlled by radio (3), the foo-fighters keep formation with the planes, even when they dive, climb, or take evasive action. "But they don't explode of attack us," Meiers said last week. "They just seem to follow us like will-o'-the-wisps. (4)"
Probably related to the silvery balls seen by daylight pilots (NEWSWEEK, Dec. 25, 1944), the foo-fighters so far apparently baffle intelligence officers. Possibly they are the results of a new anti-radar device which the Germans have developed (5). On the other hand, they may be the exhaust trails of a smaller model of the radio-controlled Messerschmitt-163, a rocket-propelled flying wing.
Day bombers have met the Me163, which has an explosive charge in the nose and is apparently designed to crash into Allied planes. When one pilot closely inspected foo-fighters tagging him, however, he detected nothing but the spheres. (7)
[*] The name comes from the "Smokey Stover" comic strip.