The battle for profitable passenger routes between U.S. and Japanese airlines has gone to the negotiating table with both countries' carriers in an argumentative mood.

Japan Air Lines wants a bigger slice of the American market. Such American giants as Pan American World Airways and Northwest Airlines are hoping to keep JAL out and preserve the status quo. U.S. charter flight companies are angling for an opening into Japan.

At stake is a 25-year-old air transport agreement, signed in the closing days of the American occupation.The Japanese government maintains it is full of inequalities that still favor U.S. companies.

Delegations composed of industry and government representatives sat down last week for a brief opening session of what is expected to be two weeks of hard bargaining.

None of the major issues has been settled - or even seriously discussed, in Japan's view - during the four previous meetings in the past year.

The meetings are accompanied by high-powered public relations campaigns and bellicose statements from the two nations' airlines, each charging the others unfair advantages in the designation of routes and the rights to carry passengers to and from third countries.

"All JAL wants is equality," said Georffrey Tudor, an official of that airline which is nearly half-owned by the Japanese government.

"There is no inequality," countered Reginald Jenkins, vice president of Northwest. "All they (JAL) ever want to talk about is the shellacking they claim they're getting.

"They aren't prepared to give anything in return. They want more (landing) points in the states and the right to fly on beyond, and each one would take money out of American pockets. We don't think anything justifies giving JAL more economic benefits."

JAL wants to expand its rights to fly to 12 U.S. cities - five more than they serve now. It wants access to a piece of the increasingly lucrative markets in Chicago, Seattle, Houston, Dallas/Fort Worth and Miami.

The American lines' routes to Japan are tied into 19 American markets and some of them - like Northwest's Chicago Tokyo run - are uncontested monopolies, JAL argues.

The U.S. airlines counter that they are restricted to only three airports in Japan and that their passenger capacities are limited because wide-bodied 747s are not permitted into one of them. Osaka.