It is coming: First Boeing 747-400 in Delta's Livery

Delta will be swapping some Northwest and Delta planes to best fit its routes with passenger demand.

The biggest airplane in Northwest Airlines' fleet -- a Boeing 747-400 -- will be the first aircraft to be painted in the red-white-and-blue color scheme of Delta Air Lines, which acquired Northwest last week.

Getting the right airplane on the right route is one of the bedrock elements of the Delta-Northwest merger, which will create the world's largest airline.

Delta executives did not disclose the routes that will be affected by the fleet changes. But Glen Hauenstein, a Delta executive vice president, said the ability to move planes to where they are needed is the "key driver" in reaching the merger's financial goals.

The 747, which seats 403 passengers, is one of Northwest's wide-body planes and it is expected to be flown on some of Delta's routes next year. One possibility is operating 747s on an Atlanta-Tokyo route. Delta's largest hub is in Atlanta, while Northwest has a major hub in Tokyo.

It will take some time to migrate the brand. But Northwest customers will begin to see changes in the coming months, such as the addition of blue leather seats on Northwest planes and the appearance of Delta's food offerings on Northwest flights.