A glitch within a schedule system has left thousands of American Airlines flights without pilots assigned to them during the holiday time, read a post titled "Holiday Scheduling Failure" on the Allied Pilots Association site.

Up to 15,000 flights are in jeopardy of being cancelled between December 17 to December 31.

"Today, management issued an update detailing the 'significant holes' in the operation and unilaterally invoked a solution for crewing affected flights," read a post that went live at 6:29 p.m. Tuesday. "Management’s actions are in direct violation of your contract."

In reaction, the APA, which represents about 15,000 American Airlines pilots, has filed a Presidential Grievance, according to the union's post.

"Because management unilaterally created their solution in violation of the contract, neither APA nor the contract can guarantee the promised payment of the premium being offered," wrote the union.

On their Twitter feed, American Airlines responded to several inquiries about the news by saying the airline had no plans to cancel flights.

“We are working diligently to address the issue and expect to avoid cancellations this holiday season," read a statement from American Airlines. "We have reserve pilots to help cover flying in December, and we are paying pilots who pick up certain open trips 150 percent of their hourly rate – as much as we are allowed to pay them per the contract. We will work with the APA to take care of our pilots and ensure we get our customers to where they need to go over the holidays.”