The main objective, Robinson explains, is to coax customers who fly most of the time on Delta to go even further on the airline. So if a flight from Newark on United is more convenient, they'll take one that leaves two hours later on Delta to get those fat mileage rewards. Garnering more of that—say, 20% of the business they now give to United or American—could substantially raise profits.
In recent years, Delta has developed a reputation for going first, and making it work––notably by orchestrating the first big merger among the majors with its purchase of Northwest. Delta's out front again on this one. The old question may apply: If it's such a great idea, why didn't another major do it years ago?