Project Blue Book: aliens or not?

UnprovenNot explained, but no evidence it is alien either. Usually too little data.

The claim

"The Air Force studied thousands of UFOs and couldn't explain hundreds of them."

The Air Force ran Project Sign (1948), Project Grudge and then Blue Book to investigate reports after the 1947 wave.

Blue Book logged 12,618 sightings; 701 were left "unidentified".
Its conclusions: no report showed a threat to national security, no evidence of technology beyond ours, and no evidence that any sighting was an extraterrestrial vehicle.
The 1969 Condon Report from the University of Colorado, reviewed by the National Academy of Sciences, concluded further study was unlikely to advance science.
Critics, including Blue Book's own scientific adviser J. Allen Hynek, said many cases were dismissed too quickly.

Unidentified usually means too little data. The 701 cases are mostly short sightings that can't now be re-examined. Weigh the explanations and vote.

Unproven Real unexplained reports, but no evidence of alien craft.

Checked 31 October 2026. Spotted a newer source? Tell us.

Our summary of the main hypotheses, with what supports and what counts against each one.

Ordinary things, too little data to identify
For Most of the 701 unidentified cases were short sightings by single witnesses; with more data, most cases were solved.
Against Some cases had multiple witnesses and radar.
Some cases were brushed off too quickly
For Even its own adviser, J. Allen Hynek, said Blue Book was more about public relations than science.
Against Being dismissed carelessly doesn't mean the case was anomalous.
Secret aircraft like the U-2 and A-12
For The CIA has said many 1950s and 1960s sightings were its spy planes, which flew far higher than any known aircraft.
Against Explains a share of cases, not all.
Some were alien craft
For A residue of well-witnessed cases was never explained.
Against In 17 years no physical evidence, photo or radar track ever held up.