Ananova:

An investigation has been launched by airline officials after a pig managed to travel in first class on a flight in the US.

The 300lb pig sat alongside passengers on a USAirways flight from Philadelphia to Seattle after its owners convinced the airline the animal was a "therapeutic companion pet".

An internal incident report said the owners claimed they had a doctor's note that required them to fly with the animal.

In a bizarre episode that rattled flight attendants and embarrassed airline officials, the pig was helped into the cabin of the Boeing 757 by four people and travelled with 200 other passengers on a six-hour flight across the country.

The airline is not amused over the incident, reports the philly.com website. "We can confirm that the pig travelled, and we can confirm that it will never happen again," said USAirways spokesman David Castelveter.

The pig's unidentified owners were described as two women, one in her 30s, the other elderly. One told the agent the pig weighed just 13lbs. Witnesses said the women exhibited no obvious impairments.

USAirways policy allows passengers to fly with so-called 'service' animals, usually trained guide dogs, and, though flight attendants objected, the incident report says USAirway's legal and consumer affairs departments cleared the pig for takeoff.

The pig was seated on the floor, in the first row of first class and, because it was so big, much of its bulk extended into the aisle.

It wasn't until the aircraft taxied into Seattle airport that the pig wreaked havoc. Squealing loudly, it ran loose through the aircraft and tried to enter the cockpit. It finally found refuge in a food galley, where it refused to budge until finally someone lured it out with food.

Federal Aviation Administration officials in Seattle said they were not familiar with the incident, but have vowed to investigate.