American Airlines and its pilots have reached a preliminary agreement for a new four-year labor contract after months of tense negotiations, a milestone for the country’s biggest carrier.

The terms of the deal weren’t disclosed but are likely to include raises as the industry faces a pilot shortage and aviators seek better pay after the Covid-19 pandemic paused new contracts for years.

American Airlines CEO Robert Isom said in March that a new four-year deal could include cumulative raises of 40%.

American’s roughly 15,000 pilots would still need to ratify a tentative agreement.

“We’re pleased to have reached an agreement in principle on a new four-year contract with the Allied Pilots Association (APA) that provides our pilots with pay and profit sharing that match the top of the industry with improved quality-of-life provisions unique to American’s pilots,” an American spokeswoman said in a statement.

Negotiations across the industry have been tense. American’s pilots recently authorized the union to call a strike if an agreement couldn’t be reached.