'Harrowing': Expert stunned as American Airlines passengers stand on wing of burning plane

Photos and videos of American Airlines passengers standing on the wings of a burning plane at Denver International Airport floored a CNN aviation expert, who called the ordeal "harrowing."

Kaitlan Collins, host of "The Source," showed multiple videos late Thursday of the plane sitting on the tarmac of the airport and thick dark smoke billowing out as a passengers lined up on the wings.

"Look at what you're looking at here," Collins exclaims to viewers. "Passengers standing on the wings of the plane. Some of them carrying their bags as they seem to be trying to evacuate this plane."

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Emergency responders can be seen racing to the plane in the videos.

Collins said, citing the FAA, the Boeing 737 was headed to Dallas from Colorado Springs but diverted to Denver due to vibration.

"It's just a remarkable scene given what has been playing out over the last several weeks with so many different aviation incidents," she said.

Aviation correspondent Pete Muntean joined Collins' show and said the flight left around 6:30 p.m. Eastern Time before experiencing "some sort of engine vibration."

"There was apparently an engine fire while the airplane was on the ground and then they were able to at least, it sounds like, put it out. Still unclear right now if anyone was injured in this. Relatively harrowing for folks to end up there on the wing while the plane is on fire," he remarks.

Muntean speculated that the smoke was coming from the right side, hence why passengers evacuated out of the left side.

"That's clearly a much safer spot, although very, very, smoky. It's not very clear whether they're completely in safety there," he added, noting the wing is about 10-15 feet off the ground, and doesn't make for an "easy jump."

Muntean flagged there appeared to be dark smoke, and said "that's not a good sign."

"It's much thicker than the grey smoke. Looks to me like the fire crews got there and were putting it out while we were seeing some of this grey smoke imagery. Black smoke is usually the worst possible sign because it's much more thick and is actively burning," he said.

Watch the clip below or at this link.