Anderson will become executive vice president at UnitedHealth on Nov. 1.
The board of directors of Northwest's parent, Northwest Airlines Corp., elected Northwest president Doug Steenland to the additional position of CEO, effective immediately.
Anderson will remain on the Northwest board, the airline said.
"For the past three years, Doug Steenland and Richard Anderson have led this company through the most difficult period in the history of the airline industry," Northwest chairman Gary L. Wilson said. "Together, they set the strategic direction of the company, which has positioned Northwest as the strongest of the legacy carriers."
UnitedHealth's CEO, William McGuire, called the addition of Anderson "exciting, because he has extensive operational experience, particularly in areas such as technology, consumer services and products, and operating efficiency."
Anderson, 49, a former Texas prosecutor, assumed the top job at Northwest in February 2001. He took over from John Dasburg at the nation's fourth-largest airline when the country was in a recession and faced such challenges as steep passenger declines after the Sept. 11 terror attacks and competition from low-fare carriers.
Despite the obstacles, Anderson told the Star Tribune, which reported on the move in Friday's editions, "It's been a great run."
Steenland's biggest challenge, he said, will be cutting labor costs. "Everything else is in great shape."
Steenland told the Minneapolis Star Tribune that employees, investors and customers will see no major change in overall direction.
"The airline strategy is set. There's no need to rethink it," Steenland said.
Steenland, 53, joined Northwest in 1991 as vice president, deputy general counsel.
As part of a cost-cutting drive, Northwest has been seeking to cut pilot compensation by $300 million a year. The pilots have offered $200 million.
"They come and they go. Hopefully they make a contribution while they're here and then they move on," said Mark McClain, chairman of the Northwest branch of the Air Line Pilots Association (news - web sites). "We'll work with whoever we need to work with to do what makes sense for Northwest pilots."
Jim Atkinson, president of the mechanics union local at Northwest, was critical of Steenland's appointment. Atkinson told The Associated Press he was disturbed to see Steenland and Anderson say "everything else is running fine but we need to get labor costs in hand."
Atkinson said Steenland was familiar to the union, often appearing with Anderson to answer questions at employee meetings.
"It's one thing to sit and answer questions," he said. "It's another to actually be in charge of the company."