United Airlines Holdings Inc. and its pilots’ union reached in principle a new labor agreement that is the richest ever at a U.S. carrier, ending more than four years of negotiations.

The agreement will result in about $10 billion in value over the life of the contract, the Air Line Pilots Association said in a statement July 15. The deal will provide pilots a pay raise of 13.8% to 18.7% upon signing and amount to a cumulative increase of as much as 40.2% over the life of agreement, according to the union. 

The agreement also details other improvements to areas such as quality of work-life, job security, work rules, retirement and benefits, according to the statement.

The company confirmed it reached a four-year agreement with ALPA, saying that the deal, once ratified, “will deliver a meaningful pay raise and quality of life improvements for our pilots while putting the airline on track to achieve the incredible potential of our United Next strategy.” 

The new deal will help ease pressure on United, which has recently come under criticism after a series of delays and cancellations to flights, even as it experiences soaring demand. Chief executive officer Scott Kirby said in an interview that overall demand is strong enough to withstand even a moderate economic recession.

Carriers are grappling with higher costs, particularly on the labor front. American Airlines Group Inc. reached a preliminary agreement in May that would add $8 billion in additional costs, and pilots will begin voting on the contract later this month. That came after Delta Air Lines Inc.’s aviators approved a new contract with a four-year term.

United and pilot union negotiators will work to complete the final language in the coming weeks. The union’s Master Executive Council will vote to determine if it becomes a tentative agreement that the group will then put up for ratification, according to the statement.