Southwest Airlines Co. and a union representing its flight attendants reached a tentative contract deal after more than three years of talks.

Terms of the agreement won’t be disclosed until it’s endorsed by the board of Transport Workers Union Local 556, the labor group said in a statement Friday. The accord also must be approved by the carrier’s 14,500 flight attendants.

Southwest, the largest discounter, reached a tentative pact with its pilots on Aug. 29. If approved, the contracts will settle uncertainty about the carrier’s future operating costs. The Dallas-based airline has sought to secure productivity gains in exchange for improved pay and benefits.

TWU 556 and the Southwest Airlines Pilots’ Association were among four union groups that backed no-confidence votes last month against the carrier’s chief executive officer, Gary Kelly, and its chief operating officer.

Dates for a ratification vote for flight attendants haven’t been set, Southwest said in a statement.

“I am pleased that we have reached this tentative agreement which, if ratified, will allow us to continue rewarding the many contributions that our flight attendants make to the success of Southwest Airlines,” Sonya Lacore, vice president for cabin services, said in the statement.

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Photo Credit: A Southwest Airlines jet gets ready to land at Tampa International Airport. The airline may finally have a deal with its flight attendants union. Skip O'Rourke / Associated Press