Tokyo's new international airport may or may not open on Saturday as scheduled, but the anxiety of waiting to see is a source of many headaches in the airline and travel businesses here.

With an alliance of radicals and farmers threatening a last-ditch offensive to keep the airport closed, the airlines are besieged with calls from nervous passengers who are booked on the first flights in and out. Some are conceling out or switching to flights that leave from another major international airport at Osaka.

The airlines are trying to reassure them that all is well and that planes can fly safely to and from the new facility 40 miles from Tokyo, but they are doing so with fingers crossed.

"Until it starts operating we can't really tell what is going to happen," an official of one foreign airline acknowleged.

The airport's opponents, who have fought an often bloody battle for 12 years to keep it closed, are doing all they can to escalate the war of nerves.

Issaku Tomura, chairman of the Airport Opposition League, issued a broadside declaring that the airport at Narita is "too dangerous to use" and blaming the government of Prime Minister Takeo Fukuda for risking the lives of foreign travelers.

"For the government to push ahead at this stage is to court tragedy," declared Tomura, who suggested that guns of the police, not his own group's threats of violence, were the major source of danger.

Yesterday, another opposition leader, Hajime Atsuta, added a new nerve-fraying note certain to frighten prospective passengers. He said that seven years ago his followers had dug a 65-foot-long tunnel beneath the land where the airport's only runway is now located.

The tunnel is still there, 22 feet underground, and is likely to cause accidents as the runway gradually sinks under the weight of planes, he said.

Airport officials disputed Atsuta's claim, saying that they had filled tunnels with concrete and pilings, but they promised to check again, anyway.

All week long authorities have been watching two structures near the airport which in the past have been used by protesters to stage violent assaults. The police have not taken them, however, hoping that a trace can be negotiated before Saturday's official opening. The radicals and farmers have refused so far to call off their threatened disruption and have scheduled a mass rally outside the airport Saturday morning.

Meanwhile, passengers, agents and airlines wait in dismay and anxiety as newspaper headlines hint at possible disasters this weekend.

Toshio Tominagi, spokesman for Japan Asia Airways, said 10 to 15 passengers a day call asking to have their bookings switched from flights leaving Narita to those departing from Osaka.

When the airline announced March 17 tha tit would use Nartita's facilities, 30 percent of booked passengers canceled immediately, he said. When the airport failed to open because of destruction to a control tower on March 26, most of the passengers who canceled rebooked since it meant they could still leave safely from Haneda, the present airport.

Many passengers who had booked flights in June suddenly switched to early May departures to beat the Narita opening, said a spokesman for the nation's largest travel agency, the Japan Travel Bureau. Many others scheduled to leave in the next few weeks are asking to fly out of Osaka, he said.

The nervousness increased when two major foreign airlines, British Airways and Pan Am, were quoted as saying their flights would not risk Narita. Officials of both subsequently said they had been misquoted and said their flights would indeed use Narita.

In Cologne, West Germany, directors of Lufthansa agreed to use Narita only if that airport is in a normal state one hour after it opens Saturday, according to the Kyodo News Service.

The government has canceled plans for a mammoth opening-day ceremony which was to have included a speech by Fakuda. Instead, only a small gathering will be held and Fukuda will not appear, apparently because of security reasons.

The airlines are insisting on maximum security. Only passengers will be permitted inside the grounds initially and all check-in baggage will be searched for explosives and then bound up to prevent reopening, a procedure normally used only at airports notoriously short on security procedures.