WINDSOR LOCKS, Conn. -- This was a pig that truly could not fly.

The pig was ordered off a U.S. Airways plane at Bradley International Airport in Connecticut on Wednesday after crewmembers determined the animal had become disruptive, Laura Masvidal, a spokeswoman for U.S. Airways parent American Airlines, said Friday.

The pig had been brought aboard the flight by a passenger as an emotional support animal, Masvidal said. She said both the pig and its owner left the aircraft before it took off. She had no other details and did not immediately know where the flight was headed.

Jonathan Skolnik, a University of Massachusetts professor who was on the flight, said he initially thought the female passenger was carrying a duffel bag. Then he smelled a stench.

"It's no duffel bag but a rather stout PIG ... on a leash," he said in an email sent to The Associated Press. "Am I dreaming?"

The woman sat next to him and tethered the pig to the armrest, Skolnik said.

"Oh no, it gets worse: the pig is incontinent," he wrote.

The passenger scrambled to keep control of the pig while trying to clean up its mess, Skolnik said. Then the pig began running back and forth, he said.

Emotional support animals are allowed on commercial flights under U.S. Department of Transportation rules as long as they are not disruptive, Masdival said.