The department said JAL may continue its service between Honolulu and Sendai, a business and industrial area northeast of Tokyo, until Sept. 20.
JAL's original authority on the route expired in October but JAL was allowed to continue to service Sendai-Honolulu with two flights a week, despite an objection from United Airlines.
United is seeking additional Japan rights and wants Japan to grant it those rights before JAL is allowed to increase services.
In addition to extending JAL's Sendai-Honolulu rights, the Department of Transportation said Friday that it also approved a JAL application to increase the service to three flights a week.
Honolulu-Sendai is also a goal for the Continental Airlines subsidiary that flies Continental's Hawaii-Japan route, now restricted to one weekly flight between Honolulu and Tokyo. Continental Micronesia wants four Honolulu-Sendai flights a week.