An unruly pig and its owner were escorted from a US Airways flight after it began defecating on the floor and squealing uncontrollably, a passenger has told Mail Online.

Rob Phelps was travelling from Hartford, Connecticut, to Washington's Reagan Airport for Thanksgiving on Wednesday morning when he saw the animal being led into the cabin on a leash.

The 65-year-old described how the 80-pound pig was screaming 'three times louder than a child' as its female companion coaxed it down the aisle with her feet because it struggled to move on its own.

'It was ridiculous,' he said. 'It started to smell and flight attendants told her to clean the mess up.'

Ordeal: A passenger has described how a pig that was escorted from a US Airways flight was defecating everywhere and squealing uncontrollably, forcing flight attendants to escort its owner off the plane

Interaction: Rob Phelps, 63, described how the woman was talking to the pig like a human during the ordeal, calling it a 'jerk' for not behaving. He added that the pig weighed around 80 pounds

Mr Phelps from Havenville, Western Massachusetts, who was with his wife at the time, said after five or ten minutes a number of passengers began to complain as the pig got more and more distressed.

He added that during the encounter the woman was talking to the animal like a human being, calling it a 'jerk' for not behaving.

She had been allowed to take it onto the plane for 'emotional support', based on guidelines released by the Department for Transportation.

Staff realized it wasn't going to work, so the animal and passenger were led out of the cabin.

Mr Phelps said that they did not encounter the pig until they boarded the plane, saying everything was normal.

Describing the moment passengers saw the creature, he said: 'There was instant silence. There was a mixture of controllable laughter and shock. You couldn't write this.

'I have seen dogs and cats in cages on a plane - but never a pig.

'This was not a small pig. When she held it over her shoulder it reached her waist.

'I don't even know how it got through. You have the TSA and intense security and yet it still was let on board.'

Mr Phelps said that the pig was the only thing the rest of the travelers spoke about the rest of the flight, and he was still laughing about it when he sat down for his turkey on Thursday.

American Airlines, the parent company of US Airways, said the woman had the pig as an emotional support animal - which is allowed under Department for Transportation guidelines

In 2012 it was revealed that the Department of Transportation had certain guidelines allowing animals, including pot-bellied pigs, could be taken on flights.

Along with monkeys and miniature horses, they could be designated as 'Emotional Support'.

Transportation officers would have to determine whether the animal is permitted on the plane by running through a list of guidelines.

Pigs are favored service animals for people allergic to dogs. Guidelines suggest they are intelligent companions and attuned to dangerous situations.