Ticket agents, gate workers and other service workers at US Airways have won the right to join the Communications Workers of America after a lengthy battle with the Arlington, Va.-based airline, union officials said. Of the 7,806 workers eligible to vote, 5,215 cast ballots in favor of the union, according to the National Mediation Board, which counted ballots. About 10,000 workers will be covered by the union. The vote was ordered in June by the mediation board after two previous votes. In a vote held Jan. 30 1997, the Communications Workers fell short of a majority but appealed to the mediation board. The board ruled US Airways had tainted the election by holding employer-employee discussions and ordered a second vote. On Sept. 29, 1997, a majority of workers voted in favor of unionizing. The airline sued in U.S. District Court and lost, but a U.S. Court of Appeals subsequently ruled in favor of the airline and set aside those results. That threw the matter back to the National Mediation Board, which ordered the third vote.