The biggest low cost carrier in the United States, Southwest Airlines, has asked a federal mediator to step into its long running contract dispute with the company`s flight attendants.

Dallas-based Southwest has been negotiating with its 7,200 cabin crew for 16 months but talks between the two sides broke down last month.

James Parker, the airline`s chief executive, said that Southwest was committed to negotiating a new contract. “Unfortunately, it no longer appears that this is possible without outside assistance. This is why we have requested the assistance of the National Mediation Board,” Parker said.

The flight attendants, who are pressing for a better pay deal, said they were disappointed with the airline`s call for a mediator. Their existing contract expired in June this year.

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