It doesn't have the same high visibility as do other issues affecting US-Japanese relations, such as automobile imports and defense. But to negotiators sometimes it seems just as intractable.
At issue is an effort to revise the 28-year-old commercial aviation treaty between Japan and the United States.
So far this year the two sides have had two intense but essentially fruitless negotiating sessions. Talks were scheduled to resume again in Washington this week.
American negotiators came away from the last session in Tokyo puzzled and disappointed about the Japanese position on revising the treaty.
"We thought we were taking care of their concerns," said one State Department official about the US offer of additional landing rights and privileges in this country.
He said the United States is prepared to offer Japan Air Lines (JAL) landing rights in 14 cities -- double the number now -- plus the right to pick up passengers in New York and fly them to Latin America.
The Japanese, he said, continue to insist that the present treaty is "imbalanced" and appear to want to solve that problem by cutting down on American flight activity in Japan rather than increasing their own flights to the US.
Under the existing treaty JAL serves only three mainland US cities -- San Francisco, Los Angeles, and New York. It has limited "beyond" rights; that is, the privilege of picking up passengers in the US and taking them to other countries.
US airlines have landing rights in Tokyo, Osaka, and Okinawa for three passenger air carriers, plus unlimited beyond rights from Japan.
Americans claim the situation isn't as unbalanced as it seems on the surface, pointing out that JAL carries 47 percent of the two-way traffic, compared with 45 percent for all US carriers combined. (The remainder is carried by third-country airlines.)
The issue is complicated by a pending request by United Airlines to serve Tokyo and Osaka from Seattle and Portland, Ore.The request has the full blessing of the US Civil Aeronautics Board but is being held up in Tokyo pending the outcome of the treaty negotiations.
The Japanese are said to be concerned that United, with its huge domestic network, could cut into JAL's market share if it were given permission to fly to Japan.
US negotiators have made it clear they consider United has the right under the existing treaty to fly to Jap an.