American Airlines has sued three mechanics unions, alleging they violated the law by urging aircraft mechanics to act together to cancel and delay flights that impacted 125,000 people.

American is asking the U.S. District Court for the Northern District of Texas in Fort Worth to issue a preliminary injunction to stop the union’s “illegal slowdown,” noting that the very busy “summer flying season” begins May 23, and the negative impact of the slowdown will increase dramatically.