This Airline Wins the Most From 'Open Skies'

Northwest will use slots leased from its partner, KLM, part of Air France KLM(AKH Quote). Their relationship, which goes back to 1993, has long been considered a model, providing antitrust immunity and revenue sharing that minimizes conflict.

"We split everything in the joint venture in half. Half the airplanes go red, half go blue," said Liu, referring to the two airlines' colors.

The arrangement definitely works for KLM, which previously used its slots to fly small planes to Rotterdam and Eindhoven in the Netherlands.

"It's far more interesting to use them to connect Heathrow with Minnesota and Detroit and with Seattle," says KLM spokesman Bart Koster. "What makes it more interesting is that you get more revenue and higher yields."

March will bring an additional bonus, when British Airways(BAB Quote) will move to its new Heathrow terminal and KLM will take over the terminal they now share.

"That means we can make terminal four a Skyteam terminal, and all of a sudden we will have a secondary hub in Europe," Koster said. Skyteam carriers will operate 49 daily Heathrow flights in the summer of 2008.

To be sure, easier Heathrow access has a drawback.

"Anytime you liberalize a market, there is increased opportunity for competition, and you see falling yields," said Morningstar analyst Brian Nelson. "At the same time as you see Northwest's European expansion, you're seeing others expand internationally as well, and all of those airlines will face a dilution of ticket prices in 2008. Airlines always compete away their profits."