Originally Posted by
Guy Betsy
Each ticketed issued sends an automatic message to the airlines. When a certain pattern of city pairs are booked more than a few times over a course of time, the airline is alerted of this irregularity. So it doesn't matter if you don't call, the airline will eventually know.
'Eventually' is the key word. Many of these fares only last a few hours anyway, but calling can alert an agent who may follow-up and shut the fare down sooner than might otherwise have happened - especially if someone notices the fare at 0200 or on a weekend.