Only recently have I come across the delicious term Foo Fighter.
foo fighter: Any of various unidentified lights encountered by airborne forces during the Second World War (1939-45), interpreted variously as enemy weapons, natural phenomena, or alien spacecraft. –OED
According to a lengthy and informative article at Answers.com, foo fighters were seen at sites all over the world during World War II:
1941: Indian ocean:
1942 Java Sea, Solomon Islands
The etymology of foo fighter is uncertain:
The term is generally thought to have been borrowed from the often surrealist comic strip Smokey Stover. Smokey, a firefighter, was fond of saying, “Where there’s foo there’s fire.” (This “foo” may have come from feu, the French word for “fire”, or Feuer the German word for “fire”, or from Smokey’s pronunciation of the word “fuel”.) A Big Little Book titled Smokey Stover the Foo Fighter was published in 1938. Foo may alternatively have come from either of the French words “faux” meaning “fake”, or “fou,” “mad.” –Answers.com
The term “flying saucer” to describe an unidentified flying phenomenon dates from 1947.
The term Unidentified Flying Object dates from 1950; the first documentation of the abbreviation UFO is from 1953. The abbreviation led to the coining of the unlovely word Ufology: “the study of UFOs.”
Perhaps because UFO carries connotations of craziness, a new acronym has come into use: UAP, “Unidentified Aerial Phenomenona.” There’s a National Aviation Reporting Center on Anomalous Phenomena dedicated to the study of UAP sightings.
Whatever you call them, these strange aerial phenomena have been around for a very long time.