"There is not going to be anything new, I think, in this report," says Air Force spokeswoman Gloria Cales. "It's going to substantiate what we've said all along."
After initially announcing it had recovered the remains of a flying saucer in 1947, the Air Force corrected itself the next day and claimed the wreckage was a weather balloon.
The sudden reversal, the exotic nature of the subject and the lingering suspicion that the government knows more than it is saying have given rise to a case that has assumed legendary proportions.
A number of books have been written about the incident, and it is considered by UFO buffs to be the biggest cover-up in U.S. history. It was also mentioned in the movie "Independence Day," which featured a super-secret government lab where scientists had studied alien cadavers for decades.
This year marks the 50th anniversary of the "crash," and it has been receiving considerable attention in the media and elsewhere. The city of Roswell, among others, aims to cash in on it.
The town's historic Plains movie theater is now a UFO museum -- one of two in town -- and has a big flying saucer on the roof.
Roswell sits on the plains east of the Sierra Blanca mountain range in southeastern New Mexico. It is in the center of the state's gas and oil industry, but it expects its population of 48,000 to double as UFO believers, researchers and the curious flock to town from July 1 through 6 for a golden anniversary of the event. Time magazine's June 23 cover story about the incident says the wreckage in question was found along a 200-yard swath of land on a sheep ranch belonging to J.B. Foster, 85 miles northwest of Roswell.
It was spotted by rancher W.W. ("Mac") Brazel and consisted of rubber strips, tin foil, wood sticks, adhesive tape, other tape with a floral design and a tough, resilient kind of paper.
Brazel thought so little of the discovery that he neglected to mention it for days. But the story has taken on a life of its own since.
It contradicted itself again in 1994, saying that the wreckage was in fact part of a device used to detect Soviet nuclear tests.
A source told Time that the wreckage came from a secret operation called Project Mogul, which launched trains of balloons carrying acoustical equipment into the atmosphere to monitor Soviet tests.
The new report, which the Air Force would not elaborate on, is also expected to address the issue of alien "bodies" which witnesses reportedly saw near the wreckage.
Among the reports was one from a Roswell mortician who claims he received an inquiry in 1947 from a nearby air base about child-sized coffins.
But according to Time those reports can be explained by another Air Force project conducted in the area in 1947.
Says Time, "Witnesses' descriptions of the 'aliens,' the Air Force notes, closely match the characteristics of the dummies: 3 1/2 ft. to 4 ft. tall, bluish skin coloration and no ears, hair, eyebrows or eyelashes."
The magazine quotes an Air Force spokesman as saying, "What quite likely happened is that people who saw these dummies mistook them for aliens."