It may be the summer of slowdowns for passengers flying on American Airlines. The airline is accusing the mechanics union of staging slowdowns in the midst of contract talks happening between the two entities.

American Airlines filed a lawsuit on Monday in the United States District Court in Fort Worth, Texas against the Transport Works Union of American, AFL-CIO, International Association of Machinists and Aerospace Workers, and Airline Mechanic and Related Employee Association.

The, American Airlines Inc. v. Transport Workers Union of America, 4:19-cv-00414-A. U.S. District Court, Northern District of Texas (Fort Worth), claims that between February and May of this year, the union's actions caused 644 flight cancelations and more than 270 maintenance delays of two hours or more, affecting the travel plans of more than 125,000 people.

The filing states: "In order to gain leverage in ongoing contract negotiations, the Union and its officers and members are engaged in the exact type of concerted behavior that courts have repeatedly held warrants an injunction to protect the traveling public." The document pointed to precedent in the Railway Labor Act, which "prohibits airlines employees from changing their normal behavior on a concerted basis in order to disrupt operations and obtain leverage in contract negotiations."

The union is viewing the lawsuit as an intimidation tactic and claims the union is trying to protect jobs while the airline offshores work to mechanics shops outside the U.S.

"Allegations of a slowdown are unfounded," International President John Samuelsen, who represents the Transport Workers Union, told the Associated Press. "This is an intimidation tactic by AA because the union is fighting back against their efforts to offshore thousands of solid blue collar Jet Mechanic jobs into South America. We will continue to battle AA to keep these jobs on USA soil and in doing so, ensure the safety of air travelers."

The TWU-IAM Association issued a rebuttal to American Airlines’ request for an injunction against the Association:

“It is unfortunate that American Airlines has chosen to abandon negotiating with its employees and instead go straight to federal court. The airline is frustrated with the Association for refusing to allow more of our maintenance and repair work to be outsourced to South America, China and Europe. We are also standing strong against cuts to our medical benefits and retirement security. Our members value American Airlines fliers and work hard everyday to ensure they have the best experience possible. The Association is ready and willing to get back to the bargaining table at any time and negotiate a fair joint collective bargaining agreement, but to do so would take a willing partner. We would much prefer to be at the negotiating table than in a legal battle brought on by American.”

American Airlines and its union have been engaged in negotiations to update a collective bargaining agreement since December 2015.

Southwest Airlines Corporation recently settled a similar dispute earlier this year. The carrier asked  a federal court to step in and halt similar behavior by airline mechanics and their union that resorted to reporting excessive maintenance issues and grounding a large number of aircraft.

The Aircraft Mechanics Fraternal Association claimed the lawsuit would  prevent workers from reporting aircraft damage. Following a warning from the FAA admonishing both sides for putting the carrier’s safety at risk,  Southwest and the union reached an agreement and were able to move forward in March.