SPECIAL CORRESPONDENT WASHINGTON - An Islamic civil rights and advocacy group has filed a complaint with the US Transportation Department over the removal of nine Muslims from a Washington-Orlando (Florida) flight. "It is incumbent on any airline to ensure that members of the travelling public are not singled out or mistreated based on their perceived race, religion or national origin," the Council on American-Islamic Relations said in its complaint. Meanwhile, AirTran Airways on Friday apologized for the incident, which occurred Thursday at Ronald Reagan Washington National Airport, saying it was a "misunderstanding." But the airline said it was only following security guidelines and that appropriate and necessary steps had been taken in the removal of the passengers. The Muslim passengers, including three children, were removed from the AirTran plane at Washington's Reagan National Airport after another passenger overheard a comment about the safest place to sit on a plane, CAIR said in a news release Saturday. After being cleared, they later were denied re-boarding and barred from other AirTran flights. "We believe this disturbing incident would never have occurred had the Muslim passengers removed from the plane not been perceived by other travellers and airline personnel as members of the Islamic faith," said CAIR Executive Director Nihad Awad. "There is a big difference between 'see something, say something,' which we all support, and reporting suspicions based solely on stereotyping and bias." The group was heading to Florida for a religious retreat. CAIR spokesman Ibrahim Hooper said his organization is working with the passengers and is considering legal action against AirTran. The Muslim Public Affairs Council also called on federal officials Friday to open an investigation. The incident aboard the plane bound for Orlando involved two families travelling together and a friend who knew the families but who wasn't travelling with them. One of the Muslim passengers, Dr. Kashif Irfan, said the confusion began when his brother was talking about the safest place to sit on an airplane, according to media reports. "My brother and his wife were discussing some aspect of airport security," he said. "The only thing my brother said was, 'Wow, the jets are right next to my window.'"