Delta Air Lines, which has narrowly fought off several attempts to unionize its flight attendants, will begin paying cabin crews during boarding, a first for a major U.S. airline and a change that is expected to increase their wages by several thousand dollars a year.

It is a notable change for U.S. airlines, where pay for flight attendants starts when all the passengers are seated and the plane’s doors close.

Delta said the change will start June 2 on all flights. In a memo to flight attendants, the airline said the new pay “further recognizes how important your role is on board to ensuring a welcoming, safe and on-time start to each flight.”

The rate of pay during boarding is 50% of regular pay rates.

The change comes as Delta plans to increase the boarding time for single-aisle or “narrow-body” planes from 35 minutes to 40 minutes, which the airline expects will increase the percentage of flights that depart on time.

Delta’s pilots are represented by a union, but several attempts to organize the flight attendants have failed in the face of fierce opposition by the Atlanta-based company. The Association of Flight Attendants, which has been gearing up an organizing campaign at Delta for more than two years, took credit for the boarding pay.

“This new policy is the direct result of our organizing,” the union said. “As we get closer to filing for our union vote, management is getting nervous.”

The union said Delta was also responding to employee anger over the longer boarding times, during which flight attendants currently don’t get paid.

Delta said the new boarding pay would be on top of 4% raises that it granted to flight attendants last month.

Unions represent upwards of 80% of workers at American, United and Southwest, but a far lower percentage at Delta.