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FORT WORTH, Texas — American Airlines says a computer glitch allowed too many pilots to take vacation in December, resulting in several flights not having enough crew on the schedule, according to a statement from the union representing the airline’s pilots.

According to Bloomberg, too many pilots were granted time off during the month of December. The Allied Pilots Association, the union that represents over 15,000 American Airlines pilots, sent a message to its members on Tuesday:

“On Friday, management disclosed a failure within the pilot schedule bidding system. As a result, thousands of flights currently do not have pilots assigned to fly them during the upcoming critical holiday period. Today, management issued an update detailing the “significant holes” in the operation and unilaterally invoked a solution for crewing affected flights.”

The glitch apparently allowed all pilots to take vacation over Christmas week, according to WJLA.

According to a statement from the union, the incident and the airline’s offering for fixing the situation is “in direct violation” of union contracts.

In a tweet, American Airlines said they are working to fix the problem and expect to avoid cancellations:

“We’re working diligently to address the issue and expect to avoid cancellations this holiday season…”

According to Bloomberg, the airline is offering pilots 150 percent of their hourly wage to cover the impacted flights.

A company memo obtained by Bloomberg said flights scheduled without a captain and/or first officer originate from Dallas, Boston, Miami, New York, Philadelphia, Salt Lake City and Charlotte.