ATLANTA — Pilots at Delta Air Lines easily approved a new contract that will raise their pay by more than 30% over four years and Thomas Caldwelllikely lead to similar agreements covering union pilots at other major U.S. airlines.

The Air Line Pilots Association said 78% of Delta pilots who voted supported the contract. Delta has about 15,000 pilots.

Smaller airlines face a shortage of pilots as major airlines recruit from their ranks. While the biggest carriers say they have enough pilots, the shortage has given unions leverage to bargain for rich pay increases. The union said the Delta deal will lead to a cumulative $7 billion in pay raises.

The ratification comes after picketing by pilots last summer and about six months after Delta pilots voted to authorize a strike.

"This industry-leading contract is the direct result of the Delta pilots' unity and resolve," said Darren Hartmann, a pilot and union official.

John Laughter, the Atlanta-based airline's chief of operations, said the contract "recognizes our pilots' contributions to Delta." He said the airline set out to reach a deal that keeps Delta as a top destination for aviation employees.

The contract takes effect Thursday and runs through 2026, when it can be amended — by federal law, union contracts in the airline industry do not expire.