UFOs have always generated intense interest and conspiracy theories about secretive government cover-ups of findings deemed too sensitive or alarming for public consumption.
France took the lead in providing UFO - OVNIs in French - information Thursday when its national space agency unveiled a website documenting more than 1,600 sightings during the past 50 years.
The website drew so much attention the host servers crashed several hours after it opened because of heavy traffic. The site is very well organized and complete, even including scanned copies of police reports.
Of the 1,600 cases registered since 1954, nearly 25 percent are classified as "type D," meaning that despite good or very good data and credible witnesses, we are confronted with something we can't explain, scientists say
Other countries collect data more or less systematically about unidentified flying objects, notably in Britain and in the United States, where information can be requested on a case-by-case basis under the Freedom of Information Act.