The flight attendants' union at American Airlines signed off late Thursday on a merger plan with US Airways.
Laura Glading, president of the Association of Professional Flight Attendants, said she signed a memorandum of understanding, which details seniority and other issues -- essentially how employees at both airlines would work together in the event of a merger.
"I hope it clears the path for a quick and efficient merger," she said.
She said she could not discuss specifics.
Meanwhile, earlier Thursday, American Airlines announced it will decide whether it also supports the merger in "a matter of weeks," CEO Tom Horton said.
In a letter to American employees, Horton said the Fort Worth-based airline is continuing to evaluate whether a merger would be in the bankrupt company's best interests.
"While I cannot give you a precise date, I can tell you that we expect to bring this to conclusion in a matter of weeks," Horton wrote.
If the two companies do combine, it would create the world's largest airline.
The flight attendants' move follows a similar action by pilots on Saturday.
The Allied Pilots Association also signed off on its own plan to combine workforces.
The Board of Directors of American Airlines' parent company, AMR Corp., is scheduled to meet Jan. 9, but it appeared a merger plan would not be ready to consider by then.
Managers of US Airways have said if they are successful in gaining control of the new carrier, they would keep its headquarters in Fort Worth and keep the American name. The US Airways brand would go away.
Analysts have said a merger is the best way for American to compete against rivals United and Delta.