London -- British and American authorities are investigating whether British Airways and other airlines fixed prices for passenger service, the airline acknowledged today.Two British Airways executives, commercial director Martin George and communications head Iain Burns, have been put on leave during the investigation, according to today's brief statement.American Airlines and Virgin Atlantic said they are cooperating with the investigation. American said in a statement that it has received a federal grand jury subpoena but was told by federal authorities that it is not a target of the investigation. Virgin Atlantic made no further comment other than to say it has put none of its executives on leave.At present, no other airlines are known to be involved in the investigation, according to wire service reports.The British Office of Fair Trading and the U.S. Justice Department are leading the investigation into allegations that airlines colluded in setting air fares and fuel surcharges.