The advent of online ticketing enabled the airlines to save money by cutting back on the number of phone agents they had to keep on duty. And, inevitably, they started charging for the privilege of making reservations the old-fashioned way. In 2004, Northwest began tacking on a $5 fee for customers who make reservations by phone and a $10 charge on tickets purchased at airport ticketing counters. American, US Airways and Continental quickly, eagerly followed suit.