A passenger on board a plane was taken to hospital after opening the emergency exit door and climbing onto the wing.
The 38-year-old man was found "incoherent and not fully aware of his surroundings", police said, after he had jumped to the ground and was captured by staff near the plane in New Orleans.
The Southwest Airlines flight had not yet taken off from Louis Armstrong International Airport at that point on Sunday night.
"There is no indication that the man left anything on the plane, nor was he found in possession of any weapons of any type," Jefferson Parish Sheriff's Office said in a statement.
"He is not expected to face any criminal charges locally, however the investigation has been referred to federal authorities. No one was injured during the incident."
Contrary to reports the man had been arrested, police said he was actually taken to hospital as officers believed he was "suffering from a mental health emergency".
Police said the flight was cancelled following the incident, but NBC News, Sky News' US partner network, reported the flight did eventually depart to its final destination of Baltimore.
Southwest Airlines said: "We commend our flight and ground crews for their swift action and apologise to our customers for their inconvenience."
The airport confirmed that there was an incident involving "a Southwest Airlines passenger's unauthorised deplaning of the aircraft".
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