A UFO phenomenon centered around Lubbock, Texas in 1951. In August and September of that year, a few hundred people reported seeing lights from silent wing-shaped craft flying in a semi-circular formation.
On August 25, some folks in Albuquerque, New Mexico reported seeing a wing-shaped object with blue lights; a few minutes later, several people in Lubbock reported about 20 of the same object, including some professors (teaching engineering, chemistry, geology, and physics) from Texas Tech University. One of the professors estimated that the UFOs were traveling 18,000 miles per hour at an altitude of 50,000 feet.
Several photographs, showing about a dozen of the lights, were taken by Carl Hart, Jr. at the end of August; the photos helped the Lights gain some national exposure.
Air Force investigators considered the possibility that the lights could have been caused by birds, but local game wardens pointed out that the most likely candidates for that time of year were plovers, which didn't tend to fly in flocks larger than six. A meteor shower was also ruled out, since astronomers didn't know of any showers that lasted for three weeks and were only visible over one geographical area.
My preferred explanation: part hoax, part mistaken identification, part mass hysteria. The Greys claim to have moved their operations out of West Texas in 1949, the Rigelians say they weren't in Lubbock at all 'til the mid-70s, and the Queen of Air and Darkness claims that the ultraterrestrials were confining their flights to the Northeast that year. Your guess is as good as mine, though...
Research from Fortean Times, September 2001, "Lighting Up Lubbock" by Peter Hassall, p. 26, and from The National Directory of Haunted Places by Dennis William Hauck, p. 342.