Aviation experts say it's not just dangerous, it's also illegal.
"I think a lot of us as airline pilots have seen a lot of strange things out of our cockpits, but a guy in a jetpack at 3,000 feet on approach to a major airport? No. That's not usual," aviation expert John Nance said.
With no video proof just yet, all we have are audio recordings of two different pilots telling air traffic control what they saw Sunday night.
"Tower, American 1997, we just passed a guy in a jetpack," a pilot said in one audio clip.
"American 1997, OK, thank you, were they off to your left side or your right side?" the controller asked.
"Off the left side at maybe 300 yards or so, about our altitude," the pilot said.
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While the FBI investigates, aviation experts say they can hardly believe it.
"This involves something we just haven't seen before," Nance said. "People in jetpacks usually don't get above about 500 feet. This guy was apparently at 3,000 feet and much too close to an inbound jetliner."
"This simply doesn't have the ability to fly up as high as 3,000 feet," aviation expert Robert Ditchey said. "Furthermore, anybody if they could do that would be insane doing it."
Jetpack technology has been around for a couple of decades and there are different capabilities depending on the design.
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In 2015, Emirates Airlines choreographed a formation flight with a jet man duo flying at 4,000 feet. They had wings strapped to their body, each with four engines -- not your typical jetpack. It was also carefully planned, as compared to this week's incident that broke federal air regulations.
"The danger here first off is to the guy in the jet pack who wouldn't last a split second if he got touched by any part of an inbound airplane," Nance said.
It could have also caused a danger with the plane itself as we've seen with drones. Just last year, AIR7 HD was hit by one while flying over downtown L.A.
"It's very hard to explain it because it's outside of almost everything," Ditchey said. "It's outside of technology, it's outside of known technology, it's outside of the regulations, and so on."
For airliners, 3,000 feet is about 10 miles away from LAX, so one of the experts believes the jetpack could have taken off somewhere from the middle of the city.