Southwest Airlines and the union representing its 8,500 ground employees have asked the National Mediation Board to jump start contract talks after 14 months of negotiations failed to produce an deal.
Transport Workers Union Local 555 called the stalled talks "disappointing," given the fact that the airline posted the highest second-quarter profit in its history. Negotiations began on July 12 last year.
"Southwest has proposed changes in our collective bargaining agreement which are concessionary in nature and entirely unacceptable to our members," union president Charles Cerf said in a statement.
The union said Southwest wants to outsource jobs, increase the number of part-time workers, and lower medical and on-the-job injury benefits.
Airline spokesman Paul Flanigan said Southwest remains committed to reaching a deal.
"Mediation is another method to assist in the collective bargaining process, and we look forward to working with a mediator to arrive at a contract that is acceptable to everyone," he said.
Both sides also used a federal mediator last year to resolve a contract dispute involving Southwest's flight dispatchers. A five-year agreement was reached in May.
Southwest and its subsidiary, AirTran, are responsible for 70 percent of the passenger traffic at Baltimore-Washington International Thurgood Marshall Airport.
More than 80 percent of Southwest's employees are union members. TWU also represents the airline's flight attendants and flight crew instructors.