The hole near the rear of the plane was found after it arrived at Charlotte Douglas International Airport on Monday from Philadelphia. The airline said there were no apparent problems during the flight. Passengers who were going to be on the plane for its next flight were put on other flights, the airline said.
Michelle Mohr, a spokeswoman for US Airways Group Inc., said the airline called the FBI because "it looked like it could have been" a bullet hole.
"It's very small," she said. "This pilot has a heck of an eye."
According to London's Daily Mail, the thought is that a stray bullet is the most likely cause, but authorities have not reached a conclusive cause:
This has prompted speculation that the jet may have been hit by a falling stray bullet.
There is no evidence at this point the flight was targeted, according to CBS.
According to US Airways spokeswoman Valerie Wunder: 'During a pre-flight inspection, one of our captains noticed a small hole in the fuselage. [...]
Amy Thoreson, an FBI spokeswoman in Charlotte, added: 'The hole extended from the jet’s skin into the cabin.
'We have a lot of physical territory to cover before we can find out how it happened, where it happened and when it happened.'
Mohr said the hole in the Boeing 737 is being repaired and the plane will return to flying on Wednesday. The plane seats 144 people, although it wasn't clear how many were on the flight from Philadelphia on Monday.
Transportation Safety Administration spokesman Jon Allen said his agency is cooperating with the FBI investigation. Charlotte airport director Jerry Orr and the FBI did not return messages Tuesday.
Federal Aviation Administration spokeswoman Kathleen Bergen said Tuesday that her agency also will ensure the aircraft is airworthy before it's put back in service, although that doesn't mean an FAA inspector will physically check the plane, she said.
"The airline has the mechanics. They have the manuals. They have skills and capability and authority to do those repairs. They do the required record keeping and then we can inspect that if necessary," she said.
Besides bullets, holes can be caused by metal fatigue or lightning. In October, a cabin lost air pressure when a hole ripped open in the fuselage of an American Airlines flight from Miami bound for Boston. In that case, the pilot had to make an emergency landing.