Northwest has been through the "most difficult period in its history"

Northwest has appointed President Douglas Steenland to the post of CEO, with immediate effect.

Mr Anderson, 49, had been at the helm of the world's fifth-largest airline since February 2001.

Last year Northwest said it was cutting 4,900 jobs, as passenger numbers fell in the wake of terror fears.

At the time, it blamed the move on a drop in passenger demand because of US hostilities with Iraq.

In recent years, it has also been under pressure because of the decline in people flying following the 11 September attacks, and competition from budget carriers.

At present, it is in negotiations with pilots and other unions to cut wages.

'Important time'

Mr Anderson will become executive vice-president at UnitedHealth on 1 November, but will remain on the NorthWest board.

"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," said Northwest chairman Gary Wilson.

"Together, they set the strategic direction of the company, which has positioned Northwest as the strongest of the legacy carriers."

Mr Steenland said it was "a privilege" to lead Northwest's 39,000 employees "at this important time for our company".