SpaceX and Twitter CEO Elon Musk referred on Sunday to a rash of UFO reports as his alien “friends” visiting Earth. A series of unidentified objects have been spotted around the world since the US shot down an alleged “Chinese surveillance balloon” and two other objects.

“Don’t worry,” the billionaire tweeted. “Just some of my [alien] friends of mine stopping by…”

Earlier on Sunday, the North American Aerospace Defense Command (NORAD) shut down a sector of the airspace above Lake Michigan, lifting it shortly afterwards. The restriction came less than a day after NORAD closed off the airspace over central Montana in response to a supposed “radar anomaly.”

Further north on Saturday, US fighter jets shot down an unidentified and unmanned aircraft over Canada. A similar object was shot down over Alaska on Friday, while a Chinese balloon was downed off the coast of South Carolina last Saturday. US officials referred to the latter object as a Chinese “surveillance balloon,” while Beijing insisted that it was a “civilian airship” which veered off course.

Speaking to Fox News, US officials described one of the objects shot down since Friday as a “small metallic balloon with a tethered payload,” while Senate Majority Leader Chuck Schumer told ABC News on Sunday that both craft were “balloons.”

Elsewhere, China’s Global Times newspaper said on Sunday that authorities in the coastal city of Rizhao were preparing to shoot down an “unidentified flying object,” while the Uruguayan Air Force said on Saturday that it had dispatched investigators to the area of Termas de Almiron to gather information on reports of “flashing lights in the sky” on Friday night.

There is no evidence that airspace closures in the US and UFO reports in China and Uruguay are connected. However, the glut of reports generated excitement among UFO enthusiasts online. 

Despite once referring to himself as “an alien trying to get back to my home planet,” Musk is skeptical about the existence of intelligent life outside Earth. In a speech at last year’s G20 summit in Indonesia, he said that humankind may one day discover “alien civilizations or civilizations that existed millions of years ago.” However, he declared in 2018 that the existence of these civilizations is not certain, and that humans should “preserve the light of consciousness by becoming a spacefaring civilization.”