Washington - A US airline on Friday apologized to nine Muslim passengers it ordered off a flight a day earlier, but defended its actions as necessary to ensure safety.

Airline officials ordered nine traditionally-dressed Muslims, including three children, off an AirTran flight that was to have left Reagan National Airport in Washington Thursday afternoon, the Washington Post reported.

Two passengers apparently complained to flight staff after overhearing a suspicious remark among the Muslim travellers, the newspaper reported Friday.

Later Friday, AirTran said it regretted the incident and apologized to all the flight's passengers, including the Muslims kicked off the flight, but said "while ultimately this issue proved to be a misunderstanding, the steps taken were necessary."

"We apologize to all of the passengers - to the nine who had to undergo extensive interviews from the authorities and to the 95 who ultimately made the flight. Nobody on Flight 175 reached their destination on time on New Year's Day, and we regret it," the airline said in a statement.

Airtran said it had refunded airfare to those excluded from the flight, would reimburse them for the costs of booking a flight on another airline and had offered to pay for their return flight.

All but one of the group were US-born citizens, and they were headed to Orlando, Florida, for a religious retreat. The group included an anaesthesiologist and a lawyer. The children were aged seven, four and two.

Airport officials later cleared the group to travel and FBI agents saw the incident as a misunderstanding, an airport official told the Post. An AirTran spokesman agreed, but added that its pilot had acted properly.

Kashif Irfan, one of the Muslim passengers, told the Post that the problem unfolded after his brother, Atif, and the brother's wife discussed the safest place to sit on an airplane. The brother apparently looked out the window and saw the jet engines next to his window.

Fellow passengers apparently felt threatened and complained to the pilot, and two federal air marshals on board then reported the matter to airport police. (dpa)