CHARLOTTE, N.C. -- ( TheStreet) -- It was US Airways ( LCC) flight attendants in Charlotte who shifted the balance against ratification of a long-awaited new contract. Now, the union is expected to wait to see what the National Mediation Board wants to do, but one labor expert said he expects a third vote on a tentative contract sometime in 2013, given the narrow defeat announced Thursday, with 51% of flight attendants opposed. "We are working on next steps and remain committed to achieving a contract US Airways flight attendants can ratify," Corey Caldwell, spokeswoman for the Association of Flight Attendants, said Friday. With about 85% of eligible flight attendants voting, the count was 2,801 against and 2,704 in favor: Revised figures vary slightly from the initial count announced on Thursday. A swing of 49 voters would have resulted in contract approval. In Charlotte, 64%, or 1,123 flight attendants, were opposed, while 611 voted in favor --- a gap of 512 votes. In Philadelphia, 834 votes, or 51%, were opposed. But in Phoenix, 1,142, or 62%, were in favor. At Washington National, 154, or 53%, voted in favor. (A one-vote discrepancy remains in these crew base numbers.) The tentative agreement would have brought a single contract following a 2005 merger between US Airways and America West, whose flight attendants (and pilots) still work under separate contracts. Both groups would have received substantial raises and job protections in the US Airways contract would have been retained and extended to America West. The airline has indicated its flight attendant costs would have increased by about $40 million annually. Apparently, one source of the opposition in the Charlotte base is that many Charlotte flight attendants formerly worked at predecessor Piedmont Airlines, where they were disadvantaged because they were not paired with pilots in scheduling. Because the tentative agreement eliminates pairing with pilots, many former Piedmont flight attendants were opposed, said a flight attendant who asked not to be named. Contract advocates say flight attendants would actually benefit from the discontinuation of pairing. The chairman of the Charlotte base declined to comment.