Airlines and airport operators complained yesterday that international passengers regularly have been jammed up for waits of two hours or more at Immigration and Naturalization booths in at least 13 U.S. airports this summer.

"It's really inhumane," said Robert J. Aaronson, president of the Air Transport Association, which represents major airlines. Aaronson said that after flying for hours, international passengers often must sit on planes for an hour before being allowed into an overcrowded area for another wait of two hours or more.

The air industry group, which also includes representatives of airports, the travel industry and British Airways, appeared to relish one particular horror story: a fully loaded Swissair DC-10 that landed at Los Angeles last week after a flight from Zurich, only to face a five-hour delay at INS booths.

That was an extreme example, they said, of problems also facing passengers at San Francisco, Portland, Seattle, Minneapolis, Chicago, Dallas-Fort Worth, Houston, Miami, Charlotte, Newark, New York and Boston. Washington Dulles and Baltimore-Washington International were not on the list.

The INS agent is the first official person any international traveler sees. The inspector checks passports and visas, and rummages through various computer data banks to determine if the traveler is legitimate or is wanted. Customs agents then inspect baggage for contraband, but the Customs Service appears to have enough inspectors, the group said.

The INS agrees that there is a problem, although the agency does not agree with the rhetoric of the airline group.

"It's been very difficult for us to keep ahead of the curve with airline traffic," said Harvey Adler, acting assistant INS commissioner for inspections. International air traffic has been burgeoning in recent years to almost all destinations, particularly to Asia.

Already, he pointed out, INS has cooperated with the airline industry to persuade Congress to alleviate the problem. In 1986, Congress allowed the INS and the Customs Service to collect a $5 user fee from passengers to pay costs of inspection. The number of INS inspectors has almost tripled since, from 557 to 1,475, Adler said. But the work load has grown faster.

In some ways, the airline group was talking to Congress as much as to the INS. For instance, the airlines and the INS agree that the $5 INS fee should be extended to air travelers from Canada, Mexico and the Caribbean, now exempted by Congress.

Said Aaronson: "Travelers from these areas still must be inspected, so it is only fair that they pay the fee like all other arriving passengers." Said Adler: That change would add $80 million to the INS budget for another 450 inspectors, and "we could definitely take care of the problem."

Adler also agreed with the airline group's call for elimination of some paperwork required by Congress, and for expansion of programs aimed at clearing passengers in advance.

"We have more things in common than we have different," Adler said.

Except for one basic question: Are there too few immigration inspectors, or do too many airliners show up at international arrival areas at the same time? "For years, we've asked the airlines to spread out their flights," Adler said.

Aaronson said, however, that airlines are restrained by scheduling problems from making any major changes. Among other things, many international passengers must make connections at either end of their international leg, he said.