GREAT FALLS, Mont. -- An airline passenger was arrested Sunday after authorities said he became unruly on a flight from Denver, at one point knocking on the cockpit door.

Authorities did not immediately release the man's name, and a federal prosecutor said it remained unclear early Monday whether the man would face any federal charges.

Sabrena Mangum, a spokeswoman for SkyWest, which operates United Express flights to and from Great Falls, said the passenger grew unruly during the flight, threatening and pushing a flight attendant and running through the aisle of the 50-seat jet.

At one point, he went to the cockpit door and began knocking on it, and got into a confrontation with other passengers who attempted to calm him down, Mangum said.

The pilots considered returning to Denver but continued to Great Falls when the man appeared to calm down. Great Falls police officers were waiting to arrest him when the plane landed there.

Barb Facile, another passenger on the flight, told the Great Falls Tribune the man appeared to be intoxicated when he got on the flight.

The man talked loudly, got out of his seat and walked around, she said, but added that he "didn't appear to be dangerous."

"For the most part, he didn't affect any passengers," she said.

Mangum said the airline is looking into whether the man was drunk when he got on board.

Great Falls Police Lt. Ernesto Rodriquez declined to discuss the incident, referring calls to federal authorities.

Assistant U.S. Attorney Carl Rostad said Monday any federal charges would depend largely on how unruly the man was and whether his actions created significant inconvenience for the flight crew or passengers. If a flight has to make an unscheduled stop because of an unruly passenger, charges are almost certain, he said.

"This may or may not rise to that level," he said Monday, noting that the FBI had not yet contacted the U.S. attorney's office about potential charges. "We'll have to look at the facts and go from there."