The Avrocar was the result of a Canadian effort to develop a supersonic, vertical takeoff and landing (VTOL) fighter-bomber in the early 1950s, the museum says.

“However, its circular shape gave it the appearance of a flying saucer out of science-fiction movies of the period,” the museum notes.

The museum shared 2007 photos of the delivery of the craft to the museum on its Facebook page a couple of days ago, which generated a fair amount of attention.

“With claims of that the US government has been clandestinely retrieving crashed UFOs for decades making their rounds these days, some images posted by the National Museum of the United States Air Force … will definitely raise some eyebrows — at first glance,” the The War Zone website said in a story this week.

But no. The craft was not (and is not) of extraterrestrial origin. Instead, it was an early effort at a circular “turbotor” vehicle.

“Flying saucers are in the news,” Brett Stole, a curator for the museum, said in an interview Friday. ”There’s a lot going on there. And this is our museum’s only flying saucer.”

Just two Avrocars were made, and the museum has one of them.

While the craft was a pioneering attempt to harness the theoretical science of “ground effect” — the force or lift provided via a downward thrust ― it didn’t quite pan out in actual flight, Stole said.

“It was one of the first vehicles to really go and lean in all the way with ground effect,” Stole said.

He added: “It really is a great attempt to take some theoretical science and try to provide an engineering solution, to get an effect that was going to be better than what we were getting at the time with conventional aircraft.”

The vehicle has been on public display since June 2008. Go see the vintage craft for yourself. Admission and parking remain free at the museum, and the hours are the same, 9 am to 5 pm seven days a week.

The entrance to the museum grounds is at gate 28B off Springfield Street in Riverside.