NEW YORK (Reuters) - American Airlines still has hundreds of flights without pilots assigned to them in December, the company said on Thursday, after a scheduling error gave too many pilots time off.

The number of flights that remain pilotless is now “a few hundred,” the airline said, compared to a peak that the carrier’s Allied Pilots Association (APA) union estimated at 15,000. American said it expects the number to continue to decrease over the next several days as more pilots agree to operate flights during the busy holiday period.

“In addition, we have more reserve pilots on hand in December than normal months, and they provide us with the ability to fly many of the trips that are currently uncovered,” spokesman Matt Miller said.

“We have not canceled any scheduled flights in December and will continue to work to ensure both our pilots and our customers are cared for.”

However, the pilots union cast doubt on the carrier’s numbers. “The Allied Pilots Association is able to view in real time December flight crew assignments for American Airlines,” spokesman Dennis Tajer said in a statement. “In fact, thousands of flights are still listed as unassigned.”

The error, disclosed to employees on Friday and widely reported this week, was an “isolated incident” and a “mistake,” Miller said. Rather than awarding a limited amount of time off based on seniority, a system blunder allotted off days to too many of the carrier’s pilots.

American has offered its pilots 150 percent of normal hourly pay to cover certain unstaffed flights.

When news broke of the mistake, Twitter users poked fun at the logistical snafu and questioned whether their own flights home would be affected.

“American Airlines (accidentally) giving all of their pilots Christmas off is one of my favorite things to happen this year,” Twitter user Blaise Schaefer wrote. “Like how are the pilots even going to get home to their families without other pilots to fly them there.”

American has a tense relationship with its pilots union. The group on Tuesday filed a grievance against management for “improperly restricting” the ability to earn extra pay on some trips and has been vocal about its concerns regarding American’s willingness to work collaboratively to resolve the issue.