The deal was rejected by 75 percent of 5,832 voting flight attendants, according to their union.
America West bought the old US Airways out of bankruptcy protection in 2005 to form the current US Airways Group Inc. But flight attendants and pilots have both continued to operate under separate contracts. That has meant the airline has to schedule them separately, in some ways running two separate airlines.
Flight attendants from the old US Airways are still working under pay cuts they took under a 2005 contract while the airline was still operating under bankruptcy protection. The rejected deal would have given them 11 percent raises.
America West flight attendants would have gotten raises of 22 percent to 65 percent, although they would have also given up vacation time and paid more for health insurance, according to materials distributed by the union before the vote.
Both groups are covered by separate units of the Association of Flight Attendants-CWA. A joint negotiating committee had unanimously recommended approval of the deal.
"We believe that to get more money out of this company would require a strike," which is difficult under federal labor rules, the committee wrote to workers on March 20.
But the next day, the council that runs the part of the union for pre-merger US Airways flight attendants ousted long-time president Mike Flores, apparently over his strong support for the deal.
On Friday, the union said it will push to restart talks, which are controlled by the federal National Mediation Board.
US Airways Chairman and CEO Doug Parker said in a written statement that the airline is disappointed by the vote. He said the company will consult with the union and the National Mediation Board "to determine the best steps going forward to one day reach a ratified agreement."
Shares of the Tempe, Ariz.-based airline fell 30 cents, or 3.8 percent, to $7.59 in aftermarket trading after the vote was released.