FORT WORTH, Texas (AP) -- The U.S. Supreme Court has cleared the way for a union-representation vote among passenger-service agents at American Airlines.

The court declined to hear American's appeal of a ruling upholding the election.

About 10,000 employees will decide whether to be represented by the Communications Workers of America. Voting is expected to start Dec. 4 and end Jan. 15.

American and the union disagreed over how much support the union needed to force an election. In February, Congress raised the threshold to 50 percent of workers eligible for a union, but the union argued that it needed only 35 percent because it requested the election in December.

The National Mediation Board, which oversees union elections, sided with the union. American sued the board. A federal district court judge in Fort Worth, Texas, ruled in American's favor, but a federal appeals court in New Orleans overturned that decision.

On Tuesday Supreme Court Justice Antonin Scalia denied without comment American's request for a hearing.

Candice Johnson, a spokeswoman for the union, said the high court's action "should put an end to the airline's attack on workers' democratic right to vote." She said agents' jobs have been outsourced and their pay and benefits cut in the past year, and a union would give them a stronger voice.

Bruce Hicks, a spokesman for American, said the airline was right to pursue the case "on behalf of the majority of American's agents and representatives who did not seek or authorize a union election."

American, a unit of Fort Worth-based AMR (NASDAQOTH: AAMRQ), has about 65,000 employees. Pilots, flight attendants and ground workers are represented by unions. AMR and American filed for bankruptcy protection a year ago.