Japan Airlines Co. announced Tuesday that it will offer code-sharing operations with American Airlines on 13 international and 14 domestic routes in Japan and the United States beginning May 10.

The code-sharing operation will cover 11 routes between Japan and the U.S., two routes between Tokyo and Asia, eight domestic routes in the U.S. and six domestic routes in Japan.

Proposed trans-Pacific operations are to include routes from Tokyo to such cities as Dallas, Boston and New York. Service from Japan to Asia will include routes from Tokyo to Bangkok and Singapore.

The two carriers plan to further expand the code-sharing to some 70 international routes and 81 domestic routes by the end of fiscal 1999.

The proposed code-sharing operation is one of the largest in the international aviation industry in terms of flight frequency, a JAL spokesman said. Code-sharing operations enable two carriers to exchange flight numbers, or codes, and use each other's planes so they can advertise more routes and save operating costs without cutting frequency of service.

JAL and AA have already joined forces on frequent flier programs and computer reservation systems.