Because of the error, Reuters reports that more than 15,000 flights from december 17 through december 31 are now without pilots.
"The system went from responsibly scheduling everybody to becoming Santa Claus to everyone", said American captain Dennis Tajer, according to CNBC.
The computer-system problem will force American to rebuild its staffing schedule, similar to what airlines must do after major weather disruptions, said John Cox, chief executive officer of consultant Safety Operating Systems and a former commercial airline pilot.
American Airlines is the largest US carrier.
We are working diligently to address the issue and expect to avoid cancellations this holiday season. "This is a crisis right now, and in that crisis, they've gone solo", he said.
American Airlines has reportedly offered pilots extra pay to work certain flights in the busy holiday travel period. Jalopnik has also asked the company that.
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.
The APA, representing 15,000 American pilots, has filed a grievance, saying the proposed solution violates its labor pact.
As of early on Wednesday, the union said management had still not reached out to discuss how best to resolve the shortage.
"I'm watching a "Grinch that stole Christmas" thing happening. And we don't want to see that happening for our passengers", Tajer said.