The unions representing mechanics at Southwest Airlines and AirTran Airways have agreed to send a tentative seniority list integration to their members as have the unions representing flight instructors, but the two flight attendant unions continue to negotiate their integration lists.

The progress on reaching an agreement for the mechanics, approximately 1,800 at Southwest and 400 at AirTran, is another significant step forward for the integration of the two carriers.

Southwest acquired AirTran in May and is aiming to have the two carriers on a single operating certificate before the end of March. Seniority list integration agreements are not a necessary component of that, but having the unions negotiate such agreements voluntarily, rather than relying on binding arbitration, helps avoid potentially divisive outcomes.

Southwest and AirTran pilots already approved a seniority list integration deal.

Southwest and AirTran mechanics will be reviewing and voting on a seniority list integration deal and an integration/transition agreement.