It was the biggest UFO sighting in years, witnessed by thousands of Phoenix residents--a string of bright lights that appeared around 10 pm on Mar. 13, 1997, before disappearing over the Estrella mountain range. The Air Force initially claimed that no warplanes were in the area. Two months later, officials from Davis-Monthan Air Force Base near Tucson cited a logbook error and confirmed that Maryland Air National Guard A-10 pilots completing a training exercise ejected leftover illumination flares near Phoenix before returning to base. "One of our guys had about 10 or so left," Lt. Col. Ed Jones told the Arizona Republic, "so he started to puke them out, one after another."



Illumination flares on parachutes form long-lasting shapes in the sky, but other airplane flares act much differently. Decoy flares spoof the sensors of antiaircraft missiles. Infrared decoys form heat signatures that resemble those of airplanes. Since some missiles discriminate targets by their movement, kinematic decoys are designed to fly as fast as the warplane that ejects them, at least briefly. "Some even come with thrusters," says Dennis Clark, a countermeasures engineer at BAE Systems. These flares extinguish quickly, which from the ground could appear to be unearthly acceleration. New missiles have sensors that use color to distinguish target airplanes, so a new type of multispectral flare changes hues to defeat them.