Southwest Airlines Co. mechanics have rejected a plan for combining their seniority list with that of mechanics at AirTran Airways.
Dallas-based Southwest last year bought AirTran for $1.4 billion.
The dispute, which is complicating Southwest's job of combining the two airlines, could go to arbitration.
Seniority often determines job assignments and pay in the airline industry.
Members of Local 11 of the Aircraft Mechanics Fraternal Association, which represents about 1,600 Southwest mechanics, voted against combining the seniority lists. Voting ended Tuesday.