American Airlines has filed a lawsuit against its mechanics unions, saying a concerted work slowdown has caused nearly 2,200 flight cancellations and delays since February and shows no signs of abating as the summer travel season begins on Friday.

The airline filed a lawsuit Monday in federal court in Texas against the Transport Workers Union of America, AFL-CIO and International Association of Machinists and Aerospace Workers (TWU). The two sides have been in contract talks since 2015 following the American-US Airways merger.

American says mechanics are unlawfully engaging in a slowdown to gain leverage in negotiations. The lawsuit says they are taking an "inordinately long time to repair aircraft'' and refusing to work overtime. It says the moves have resulted in 644 unplanned canceled flights and 1,500 delays, including 270 delays of two plus hours.

"The odds of this being random as opposed to concerted activity is less than one-in-one billion,'' the lawsuit says.

The unions did not address the allegations of a slowdown in their response on Tuesday. In a statement, the joint IAM-TWU Association said it's unfortunate American is taking them to court rather than negotiating a contract and that American is frustrated because mechanics refuse to allow more maintenance and repair work to be be outsourced to South America, China and Europe.

“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,'' the statement said. "We would much prefer to be at the negotiating table than in a legal battle brought on by American.”

American's allegations are strikingly similar to those leveled by Southwest Airlines against its mechanics union earlier this year during a bitter labor dispute. The airline, which said the maintenance delays and cancellations were costing the airline millions of dollars weekly, filed a lawsuit against the union in early March. The two sides reached a tentative contract later that month. The Aircraft Mechanics Fraternal Association announced Tuesday that Southwest mechanics overwhelmingly ratified the new contract.

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American said the alleged maintenance slowdown has intensified since the last negotiation session with the unions, overseen by the National Mediation Board, ended on April 25. The lawsuit says it is now causing an average 14 cancellations per day, compared with eight a day a few weeks ago.

It asked for a preliminary injunction against the union because the alleged campaign threatens to seriously disrupt the airline's summer travel operations.

American said an additional 2,200 flights would be canceled or significantly delayed (2+ hours) during the peak summer travel season if the slowdown persists at current levels, which would affect more than 300,000 passengers. That compares with 914 canceled and significantly delayed flights since February.

American Airlines President Robert Isom said Tuesday the airline needs the unions to stop the slowdown and said he has "full confidence'' they will.

"We need everybody pulling In the same direction, and I’m quite confident we'll get there,'' Isom said during a presentation to investors in New York.

This article originally appeared on USA TODAY: American Airlines blames mechanics for 2,200 flight delays, cancellations, warns of summer travel trouble