Southwest Airlines Co. mechanics approved a new contract that provides pay increases and a retroactive bonus, closing out more than six years of negotiations that included a lawsuit and an alleged worker slowdown.

The five-year agreement won 95% support from the Aircraft Mechanics Fraternal Association, the union said Tuesday. About 94% of eligible voters participated.

The approval removes uncertainty for the airline over costs, and ends the threat of further flight disruptions less than three months after Southwest sued the union for deliberately slowing operations. The 2,700 mechanics are the last of Southwest’s largest labor groups to secure a new contract since 2016, following pilots, flight attendants, baggage handlers and other airport ground workers.

The deal provides employees $160 million in retroactive pay as a ratification bonus, an immediate 20% raise effective April 1, and 3% annual increases each August, according to an earlier statement from the union and Southwest. The workers rejected a previous proposal in September.

‘Safety Culture’

The union’s national director, Bret Oestreich, thanked mechanics for their “patience, support and professionalism” over more than six years of talks with Southwest.

“Our focus now shifts to working together with Southwest Airlines, as we do the important work of restoring the safety culture Southwest Airlines has traditionally been known for,” the union said in a blog post.

In addition, the Dallas-based carrier secured new work rules in the contract that are designed to increase productivity.

“Our mechanics will receive well-deserved pay increases, and the company will realize additional flexibilities necessary to compete in today’s airline industry,” Russell McCrady, Southwest’s vice president of labor relations, said in an email. “This new contract benefits all parties as it takes care of our people and preserves the long-term health of Southwest Airlines.”

Legal Standoffs

Southwest sued AMFA in March, claiming mechanics were engaging in a work slowdown by grounding planes for repairs not related to flight safety, causing the carrier to cancel 2,800 flights in the first quarter and costing it millions in lost revenue. The union denied the allegation.

Aviation regulators warned Southwest and the union on March 8 that their contentious contract talks and legal fight were putting the carrier’s safety at risk. The Federal Aviation Administration urged the two sides to work cooperatively on safety issues. Southwest, which flies the most passengers on domestic flights among U.S. carriers, and AMFA reached an agreement eight days later.

In a separate lawsuit, American Airlines Group Inc. sued its mechanics’ union this week, alleging an illegal campaign to slow maintenance and increase negotiating leverage against the Fort Worth, Texas-based carrier.

On Tuesday, the TWU-IAM Association called the lawsuit “unfortunate” and said it is “ready and willing to get back to the bargaining table at any time and negotiate a fair joint collective bargaining agreement, but to do so would take a willing partner. We would much prefer to be at the negotiating table than in a legal battle brought on by American.”