Delta is experiencing an abnormally high volume of flight cancellations compared to its mainline counterparts. SAUL LOEB / AFP via Getty Images Delta canceled hundreds of flights this weekend, while American and United canceled a handful. An internal memo obtained by Business Insider shows the reason is crew scheduling. Delta is using a complex scheduling system to fill last-minute trips, which can be inefficient. Delta Air Lines is canceling hundreds of flights — far more than its competitors — and its strained scheduling system is largely to blame, Business Insider has learned. Since Friday, Delta has canceled about 500 flights, while American Airlines and United Airlines have canceled a combined total of 80 flights. Delta canceled some flights in recent days within hours of boarding. "We apologize to our customers for higher than usual cancellations this weekend due to crew resources," a spokesperson told Business Insider in an emailed statement.…