excerpt from today's L.A. Times
And the quintessential Area 51 conspiracy—that the Pentagon keeps captured alien spacecraft there, which they fly around in restricted airspace? Turns out that one's pretty easy to debunk. The shape of OXCART was unprecedented, with its wide, disk-like fuselage designed to carry vast quantities of fuel. Commercial pilots cruising over Nevada at dusk would look up and see the bottom of OXCART whiz by at 2,000-plus mph. The aircraft's titanium body, moving as fast as a bullet, would reflect the sun's rays in a way that could make anyone think, UFO
In all, 2,850 OXCART test flights were flown out of Area 51 while Slater was in charge. "That's a lot of UFO sightings!" Slater adds. Commercial pilots would report them to the FAA, and "when they'd land in California, they'd be met by FBI agents who'd make them sign nondisclosure forms." But not everyone kept quiet, hence the birth of Area 51's UFO lore. The sightings incited uproar in Nevada and the surrounding areas and forced the Air Force to open Project BLUE BOOK to log each claim.
Since only a few Air Force officials were cleared for OXCART (even though it was a joint CIA/USAF project), many UFO sightings raised internal military alarms. Some generals believed the Russians might be sending stealth craft over American skies to incite paranoia and create widespread panic of alien invasion. Today, BLUE BOOK findings are housed in 37 cubic feet of case files at the National Archives—74,000 pages of reports. A keyword search brings up no mention of the top-secret OXCART or Area 51.