A glitch in American Airlines' pilot scheduling system means that thousands of flights during the holiday season currently do not have pilots assigned to fly them. From a report: The shortage was caused by an error in the system pilots use to bid for time off, the Allied Pilots Association told NPR. The union represents the airline's 15,000 pilots. "The airline is a 24/7 op," union spokesman Dennis Tajer told CNBC. "The system went from responsibly scheduling everybody to becoming Santa Claus to everyone." "The computer said, 'Hey ya'll. You want the days off? You got it.'"