The Association of Flight Attendants union is suing Delta Air Lines, saying the carrier isn't living up to the contract that covers unionized flight attendants from merger partner Northwest Airlines.

Delta spokeswoman Gina Laughlin said the company believes the lawsuit has no merit. The dispute reflects increasingly contentious relations between the union and the mostly non-union airline as a representation vote looms.

Delta and Northwest merged in 2008, and flight attendants from Northwest are represented by a union while those from Delta are not. The combined flight attendant group is expected to vote by the end of this year or early next to determine whether all attendants will be union-represented. The union has begun the process toward an election, though one has not yet been scheduled.

In the suit filed last week in federal court in Washington, the flight attendants union said that as the election approaches, Delta "is increasingly unwilling to resolve disputes with AFA." It added that Delta "is now breaching AFA's collective bargaining agreement with increasing regularity." In the suit, the union claims it has encountered issues with health and safety violations, scheduling violations, pay violations and other violations.

The union is seeking relief from the alleged violations and an unspecified amount of damages.

"The AFA’s claims are inaccurate," Laughlin said in an e-mailed statement. "We can only presume this is meant to divide flight attendants and distract them from the upcoming representation election."

Janette Rook, president of the Association of Flight Attendants union at Northwest, said in an e-mailed statement that the union stands by its claims that the company is "not willing to abide by the contract."

"Delta inherited our agreement and is bound by its terms," Rook said.