EAGAN, Minn. (AP) _ Northwest Airlines said Friday it has agreed to an alliance with Air China to steer passengers onto each other's flights.

The deal comes after the United States and China agreed in December to allow their countries' airlines to co-promote flights. Northwest said its Air China venture is the first alliance between major U.S. and Chinese airlines.

The Minneapolis-based airline signed a preliminary agreement last week with Air China, Northwest co-chairman Gary Wilson announced at the company's annual meeting in New York.

The deal includes a code-sharing agreement, which will allow the airlines to attach their two-letter codes to each other's flights in travel agents' computers and then advertise and sell those flights as their own.

As part of the December agreement, Chinese airlines can put their codes on flights between U.S. cities, while U.S. airlines are limited to sharing codes on flights to the cities of Beijing, Shanghai and Guangzhou, said Northwest spokesman Doug Killian.

The airlines also will coordinate their connections to feed traffic to each other's flights and will initiate joint frequent-flyer programs and other promotions.

Northwest currently operates flights from Los Angeles to Beijing and Shanghai. It will begin nonstop Detroit-to-Beijing service May 1.