The agreement, which goes into effect Sept. 15, is a follow-up to a similar arrangement that Mahalo has with Hawaiian Airlines and is based on Northwest's own existing arrangements with Hawaiian.

In the code-sharing plan, Northwest's passengers traveling from or to Northwest's destination cities of Los Angeles, San Francisco, Seattle, Minneapolis/St. Paul, Tokyo, Osaka, Nagoya or Fukuoka, Japan, will ride on Mahalo within the islands if they go to Molokai or West Maui.

"We are pleased to team up with Northwest, an airline that has almost 50 years experience serving the Pacific," said Douglas Caldwell, Mahalo's vice president of sales and marketing.

Douglas Birdsall, a Northwest vice president, said the Mahalo Air connection will build on his airline's already-strong connection with Hawaii.

St. Paul, Minn.-based Northwest already has a code-sharing deal with Hawaiian, in which Hawaiian carries Northwest's passengers among the major islands, but Hawaiian does not fly to West Maui and its Molokai service is limited, Northwest said.

The airline also said its WorldPerks frequent flyer program has a new award called the Hawaiian Island Pass, which allows travel for eight days among the islands on Hawaiian or Mahalo. WorldPerks members can get the pass by trading in 15,000 of their frequent-flyer miles.