Passenger reservations agents at US Airways yesterday voted overwhelmingly to join a union after nearly a decade of pay freezes and benefit cuts.

The victory by the Communications Workers of America was the latest in a campaign by organized labor to sign up the last large group of nonunion employees at the nation's major airlines.

"Agents have sent management a clear message," said CWA President Morton Bahr. "They want representation and a contract." The union said it expects US Airways to begin bargaining immediately on a contract for the airline's 10,600 reservations agents.

Of 7,806 US Airways reservations agents who were eligible to vote, all 5,254 who cast ballots voted for CWA representation. It was the third representation election since 1992, when the CWA first began its organizing campaign at the airline.

US Airways had little comment on the election beyond making a pledge to work with the union.

In the previous elections, the union first failed to win the backing of a majority of the members, but a rerun election was ordered after federal labor officials ruled the airline's management had illegally interfered with an election.

The CWA overwhelmingly won the second election, but US Airways challenged the interference charge and asked the federal courts to set aside the election results. In June a federal appeals court ruled in favor of the company and the third election was ordered.

Under the Railway Labor Act, which governs labor relations in the airline industry, a majority of the eligible members of the bargaining unit must participate in the election for the results to count. A union then must win a majority of those voting.

The 7,806 passenger reservations agents eligible to vote in the election represent the number of agents employed at the time of the first election. Since then, the number of reservations agents has risen to 10,600.

Pay for the airline's reservations agents was frozen and benefits were cut in 1992 by an earlier management at a time when the airline, then called USAir, was suffering major financial losses. Starting pay at the time was $7.50 an hour, with the top pay rate at $17.88 an hour.

In March 1993 the company created what was known as an E-Scale for all new reservations agents. It had starting pay of $7.50 an hour and no benefits including any paid time off.

At the airline's annual meeting in Charlotte last spring, US Airways Chairman Stephen M. Wolf acknowledged the financial hardships faced by the reservations agents, but said he was unable to help them because they have been the subject of a union organizing campaign since he arrived at the company in January 1996. Under federal labor law, pay and working conditions cannot be changed while the organizing effort is underway.

In June, when the court overturned the results of the second election, the company unilaterally raised pay and benefits to levels that had been agreed tentatively to during contract bargaining by the union. Although this was illegal, CWA officials said at the time they were not in a position to further delay pay increases for the agents.

In April, the International Association of Machinists negotiated its first contract for 6,000 fleet service employees at US Airways.

But the airline's 7,000 mechanics and ramp workers, also represented by the IAM, last month overwhelmingly rejected a tentative contract agreement and the 9,000 members of the Association of Flight Attendants are currently in negotiation for a new contract.