A federal judge on Friday ordered unions that represent American Airlines mechanics not to interfere in the airline's operations.
The judge's order came after American asked for a temporary restraining order to end what it considers an illegal work slowdown by mechanics that is causing delayed and canceled flights.
Judge John McBryde in Fort Worth, Texas, said a temporary restraining order is warranted because American is likely to win on its claim that the Transport Workers Union and the International Association of Machinists and Aerospace Workers are violating federal labor law.
Lawyers for the unions did not immediately respond to an email seeking their comment.
The dispute at American is similar to a recent fight at Southwest Airlines, which also went to court against its own workers before both sides agreed on a new contract earlier this year.
Tension between the unions and American has grown since contract talks broke off in April. Despite help from a federal mediator, the two sides have failed to reach agreement on pay, health benefits, limits on American's ability to outsource maintenance work, and other issues.
American sued the unions on May 20 and sought a less urgent injunction against the unions. In a court filing, American said that in the 23 days after it filed the lawsuit, the slowdown worsened, causing it to cancel 722 flights due to maintenance delays, or nearly 70% of the maintenance-related cancellations during the previous 14 weeks.
The airline said more than 175,000 passengers have had travel plans disrupted by the slowdown.
Union officials have denied that they are encouraging a slowdown.
The unions represent about 31,500 employees at Fort Worth-based American, including about 12,450 mechanics. Some had worked at US Airways before the two carriers merged in 2013 to create the world's biggest airline.
The judge's order bars the unions and their members from participating in or encouraging interference with American's operations, including any slowdown such as refusing to work overtime if it is designed to keep planes out of service.
A trial in the case is scheduled for July 1.