Back in the mid ’70s the French set up a small government agency within their equivalent of NASA, specifically tasked with investigating these incidents. It still exists today. When something happens, there are people they can call in to assist from various specialties, depending on what’s needed. So say that there’s a case where something lands—they might need a soils expert to look at samples, they might need a plant pathologist to look at decay or burning of plants. They might need a psychologist to interview a witness to determine if this witness is hallucinating or if he is of sound mind.

They have a steering committee that meets three or four times a year to go over the data and analyze cases. In the process of that they have accumulated a lot of very interesting data; a lot of the most interesting stuff has to do with physical evidence.

France is unique in its scientific emphasis and the scientific approach. They’re devoted to doing this purely for research’s sake. In other countries—Peru, Chile, and Uruguay—these agencies are set up in the military or air force and work from an aviation safety or military point of view. The UK Ministry of Defense had a big one, but they closed it down in 2008 because they were so overwhelmed with Freedom of Information requests.

What have the French concluded?

In terms of conclusions, these people who have been doing this for a long time always seem to say that you have to look at various hypotheses. The incidents that have been well enough studied—for which there is enough data that you can eliminate the natural possibilities like satellites, or the planet Venus, or other phenomena—then they will say the same thing that other officials say which is that they think the extraterrestrial hypothesis is certainly a valid and rational one that needs to be looked at. And you have people at the highest level in France saying that, not just in the scientific community, but in the military community. That’s why as a journalist I got interested in this: because I thought it’s kind of a big deal for these guys to say this stuff.

Could you describe a favorite sighting?

That’s a tough question, because there are a bunch of really interesting ones. The case that opens up the book is a series of sightings over Belgium in 1989, ’90, and into ’91. It was an extraordinary series of events, because it kept repeating itself. Air Force Major General Wilfried De Brouwer was the man put in charge of investigating and has written a chapter in the book that brings forth a lot of information about the sightings. Over a period of a year and a half, two years, this triangular craft kept showing up again and again. They’ve got volumes and volumes of reports and drawings and audiocassette tapes of people who called in their sightings. What’s really interesting about it is that the government became very actively involved. They sent up F-16s to try to get close to the objects, they set up special radar gear, and systems by which they would activate the F-16s if certain things happened. It was very impressive that the government took it so seriously.

These things kept showing up unannounced in protected airspace, and seemed to operate with impunity. They were considered sort of invaders. They wouldn’t respond to any communication, they behaved in ways that were not like any other aircraft that anyone had ever seen, very large and silent, and very, very, brilliant lights. And they could take off with the blink of an eye, just zoom off from a hovering position—just all kinds of capabilities. They were documented, and numerous police officers and some military people as well were there and involved—seeing them, documenting them, drawing them, and talking about them.

There’s no question that this happened. And De Brouwer, a colonel at the time, did go to the highest levels of other NATO countries to find out if this was some sort of test flight by Russia or the United States, and he was absolutely told that that it absolutely wasn’t. And in fact, documents show that United States officials wanted to find out more about it from him. That’s a mystery that’s never been solved.

What sort of government documents are available on UFOs?

Clint Hendler is the managing editor of Mother Jones, and a former deputy editor of CJR.