It may have been due to a false alarm, but a bunch of American Airlines passengers had to cool their heels for hours while a new pilot was found to fly the plane out of DFW Airport last night.  Flight 1211, from DFW to Cancun, was loaded and ready to leave the gate when the pilot came on the intercom with a shocking announcement, saying he would have to leave to be tested for alcohol.  Someone, and it’s not clear who, reported that he’d been drinking before the flight.  That set in motion mandatory procedures that entail blood tests for the pilot and a search for a substitute who has to get to the airport as soon as possible. After about four hours, the flight lifted off from DFW just before 9 p.m.  Multiple sources suggest that the blood test later turned up no evidence of alcohol or drugs.  Who made the initial accusation has not been revealed.  But the same sources hint that it was a co-worker, not a passenger.