CHICAGO - The FBI is investigating what might be a bullet hole, discovered in the side of a US Airways Group Inc plane this week, the airline said on Wednesday.

The small hole in the Boeing 737-400 was found by a pilot on Monday at the Charlotte/Douglas International Airport in North Carolina.

Related readings:  France denies plane shot down in Libya  Honduras plane crash kills all 14 people onboard  Russia unveils final report on Kaczynski plane crash  At least 70 killed in Iranian passenger plane crash

"The pilot was doing his standard, pre-flight walk-around and noticed a small hole in the rear, left fuselage," said US Airways spokeswoman Michelle Mohr.

An FBI spokeswoman in Charlotte was not immediately available to comment on the investigation.

The aircraft had arrived in Charlotte from Philadelphia carrying 84 passengers and was scheduled to fly to Hartford, Connecticut, when the hole was found.

The plane, designed to carry 144 passengers and five crew members, was taken out of service on Monday and was scheduled to be back in service on Wednesday, Mohr said.