Officials Disclose a ‘Working Theory’ About Jetpack Mystery Over Los Angeles

But large groups of loose balloons can be dangerous for flights, he said.

And Mr. Young said that the number of objects and potential hazards in the air — drones, balloons, laser pointers directed at the skies — was increasing year to year. Many of these get reported each day by small airplanes or commercial flights, he said, but the size of the reported jetpack user made it a “pretty rare” safety risk.

Pilots first reported a suspicious sighting in August 2020, describing a man flying a jetpack at about 3,000 feet near Los Angeles International Airport. “Tower, American 1997 — we just passed a guy in a jetpack,” the pilot of American Airlines Flight 1997 from Philadelphia told air traffic control at the time, saying it looked like there was a person about 300 yards to the plane’s left.

The sighting started an investigation by the F.B.I. and the F.A.A. The authorities then heard of a second sighting about six weeks later, as crew members on a commercial airliner flying near the airport reported seeing what looked like a person at an estimated 6,000 feet. This July, a third sighting, at 5,000 feet, was reported by a pilot flying a Boeing 747 over Los Angeles.

“Possible jetpack man in sight,” the pilot said at the time. After air traffic controllers and pilots discussed the sighting, a pilot simply said, “We’re looking for the Iron Man.”

A spokeswoman for the F.B.I. at the time of the third sighting said that the bureau was working with the F.A.A. to investigate, but that it had not been able to validate any of the previous sightings.

While the jetpack sightings have drawn widespread attention, they’ve also drawn skepticism from companies that make jetpacks.

Most jetpacks lack the fuel efficiency to fly for more than a few minutes, which makes it difficult for them to get very high. And flying in a crowded airspace, like around a major airport, could be extremely dangerous for a jetpack user, who would risk collision with a jet or being drawn into a plane’s engine.