(Reuters) -Southwest Airlines said on Wednesday it has reached a tentative agreement with the Transport Workers Union Local 556, representing nearly 19,000 flight attendants, making it the first major U.S. airline to strike such a deal.

The union would communicate details about the agreement and the voting timeline directly to its members, the company said.

Transport Workers Union Local 556, which represents Southwest's flight attendants, has said its members have not received a pay raise in the last four years.

Southwest flight attendants have been demanding higher pay and a better work-life balance in their new contracts.

In the past two years, unions across the aerospace, construction, airline and rail industries have put up fights for higher wages and more benefits in a tight labor market.

In August, the airline reached a tentative labor agreement with the union that represents about 17,120 transport workers who handle ramp, operations, provisioning and cargo.

United and American Airlines are yet to reach an agreement with their flight attendants over new contracts.

(Reporting by Sourasis Bose in Bengaluru and Rajesh Kumar Singh; Editing by Shailesh Kuber and Pooja Desai)