AirTran Airways flight attendants ratified a new contract Tuesday that boosts their pay as they prepare for the carrier’s sale to Southwest Airlines.

The Association of Flight Attendants said a majority of members voted for the deal. Of those who cast ballots, 96 percent voted in favor of the new agreement.

The two-year deal takes effect May 1. It includes 4 percent pay increases per year and bonuses ranging from $250 to $4,100 depending on seniority, according to a summary.

AirTran spokesman Christopher White said the deal benefits the airline’s 2,200 flight attendants as well as the company.

Southwest expects to close its purchase of AirTran in coming weeks. Although the deal is expected to bring higher pay to AirTran employees, it could take a couple of years for that to happen.

Southwest’s flight attendants are represented by the Transport Workers Union. The two unions will have to negotiate how to combine seniority lists and eventually come to an agreement to combine under Dallas-based Southwest.

AirTran, which is based in Orlando but has its main hub in Atlanta, reached a new contract with pilots last year.