United Airlines' $715.5 million purchase of Pan American World Airways' extensive Pacific route network could become a new item on the list of grievances involving U.S. access to Japanese markets.

United now has all its U.S. approvals lined up and is ready to take over the Pan Am operation Jan. 28. However, the Japanese must first grant landing rights to United, and they are balking. Talks on the subject between U.S. and Japanese officials are scheduled to begin in Tokyo on Monday

Under an existing bilateral treaty, the United States has the right to designate the U.S. airline or airlines that will fly to Japan, just as Japan has the right to designate its carriers. Pan Am has held most of the U.S. designations for years, but they are now being transferred to United.

Obtaining designations is one thing; securing landing rights is another. Not surprisingly, Japan Air Lines (JAL) has been urging its government to win further concessions from the United States as a price for letting in mighty United.

Matthew V. Scocozza, the Department of Transportation's assistant secretary for policy and international affairs, said, "I am not very optimistic about a Jan. 28 startup." He said, "We've made it clear that we're not paying for something that is guaranteed in the existing bilateral."

If the game gets tough, the United States could withdraw landing rights here for JAL. "That would be an extremely distasteful step to take, but Japan may give us no recourse," Scocozza said.

George Aste, a United vice president, said, "We still intend to begin service Jan. 28. We are confident we will have approvals of the government of Japan" and nine other Asian nations that United will serve.

United is expected to provide a stronger U.S. presence in the Pacific than Pan Am did because United has a powerful, West Coast-oriented domestic route network to feed its international flights. Currently, JAL is the leading carrier over the Pacific, with Northwest Orient and Pan Am running second and third.

COMPLAINT FILE . . . People Express has been having problems with disgruntled passengers. On two days before Christmas it left a total of 280 passengers at San Francisco International Airport without rides, apparently because of overbooking. People, which says its fares are always the lowest, also leads major domestic airlines in complaints filed with the DOT.

In October, for example, People had 4.64 complaints per 100,000 passengers, the highest number among major carriers. Pan American was second with 3.7 and New York Air was third at 3.55.

TRUCKING . . . Trucking safety is a government stepchild. Responsibility is divided between two less-than-vigorous agencies, the Interstate Commerce Commission and the Federal Highway Administration's Bureau of Motor Carrier Safety, part of the DOT.

The ICC's trucking oversight since deregulation consists primarily of throwing tariff (freight rate) filings in a box. The BMCS has specialized in announcing in advance when and where it was going to set up "surprise" truck inspections. The truckers' CB radio net establishes detours faster than any highway department ever did.

But recurring stories of overturned trucks on the Capital Beltway are creating a clamor for action. The trucking establishment is trying to get out in front of the issue, while also battling administration proposals to fully deregulate trucking and abolish what is left of the ICC.

American Trucking Associations President Thomas J. Donahue told reporters at lunch yesterday that the industry's safety record "is not as good as it should be and it's worse than last year. Before we have more deregulation of trucking, we need to take a major look at safety."

ATA supports a recent legislative proposal, by Sens. John C. Danforth (R-Mo.) and Robert Packwood (R-Ore.), that would establish some sort of national drivers' license for truckers to eliminate a recurring problem of one driver holding licenses from several states to avoid suspensions.

BLOCK THAT SCAM . . . This just in, football fans! The Transportation Department, ever mindful of its responsibility to protect the consumer, warns that not all Super Bowl tours advertised by charter packagers include tickets to the game. If you simply like New Orleans, where the Super Bowl is to be played Jan. 26, it might not matter. But if you want to see football, read the ads carefully.