The economic fallout from the air traffic controllers walkout is turning out to be surprisingly light.

Travel agents, concessionaires at airports, and hotel and motel officials have felt the pinch of a sudden, reduction in the number of flights and daily airline passengers -- who probably numbered 100,000 during August. But now that the chaos has diminished and flight schedules are more certain, the economic impact is diminishing.

Reagan administration economists took a look at the situation and quickly concluded that it "is not statistically significant" in terms of the entire economy. In other words, it won't cause even a blip in the gross national product.

However, the strike and the indefinite reduction in flights certainly produced a blip in the August accounts of many businesses directly involved with serving the airlines and their passengers. For travel agents, airport concessionaires and taxi drivers, the blip may be much longer-lasting. On the other hand, a check of several major hotel and motel chains indicates their occupancy rates are climbing back to prestrike levels.

Travel agents, who normally book about 60 percent of all domestic airline reservations, have had two problems. First, they have had to rebook many flights, which has meant doing double the work for each commission. Second, they have had a flood of cancellations. The loss has averaged 60,000 commissions a day. Since each loss equals an average of about 10 percent of the ticket cost, the total has been several million dollars daily.

Virginia Rudick, manager of an Ask Mr. Foster Travel Service office in Washington, is afraid the strike is going to have a lingering effect on business, not because of the reduced number of flights, but because of the publicity concerning whether it is safe to fly -- an issue raised repeatedly by the controllers union.

"I think it is going to take a long time to restore the confidence of the public in flying," said Rudick, who has had customers canceling flights for the Thanksgiving and Christmas holidays and is waiting to see what happens in the next several weeks before filling two vacancies in her office.

In New York City, a spokeswoman for the American Society of Travel Agents professed nevertheless to see a hint of a silver lining. "In the long run," she said, "it may be beneficial, because people will realize the value of travel agents" in getting flights in uncertain and confused situations.

Initially, many hotels, especially those located near airports, were hit by a rash of canceled reservations. The Sheraton chain, for instance, had about a 10 percent cancellation rate immediately after the strike began. And, of course, there was an immediate and continuing loss of business throughout the country because fewer airline crews had to find overnight accommodations.

Now, asserts a Sheraton spokeswoman, "There is little if any impact" from the reduced flights. The Sheraton on Columbia Pike in Arlington, not far from National Airport, had a record August, she noted.

Essentially the same system-wide story is told by officials at Marriott, Hilton and Holiday Inns: some declines in business, with operations again approaching normal levels for this time of year, which is far from busy to begin with. (However, "normal" for 1981 was already depressed compared with the two previous years, with occupancy rates for the first eight months of the year down to 67 percent from 72 percent in 1980.) Hotels in a few locations, such as Chicago's O'Hare Airport, have been harder hit.

Albert E. Kudrle, director of public relations for the American Hotel and Motel Association, says that in the association's spot checks, which have included numerous resorts, "most properties are reporting business as usual. . . . I don't see there is going to be a tremendous loss . . . "

Elsewhere, Albert Rankin of Marriott Corp. said its inflight food service business is off "about 10 percent." Marriott has laid off about 500 persons, including some in the Washington area, as a result, he said.

Other firms that distribute products -- including fuel -- to the airlines are experiencing or expect to experience similar declines.

Concessionaires at National Airport, where the major air carriers are providing about 80 percent of the normal number of flights, sustained between a 10 percent and 15 percent drop in sales in the first two weeks after the strike, according to David Hess, public affairs officer for metropolitan Washington airports. Since then, Hess said, "It's coming back. Our parking lots are pretty well filled again" and other concessionaires' business is up, too.

Meanwhile, the number of complaints about noise from low-flying jets near National dropped to half the usual daily average of 15 to 20, Hess said. And for some unknown reason, concessionaires' revenues at Dulles Airport went up, not down, by about 10 percent in August.

One likely beneficiary of the airlines' woes, Amtrak, turns out not to have benefited much at all. An Amtrak spokesperson said virtually all Amtrak's long-distance trains were already booked solid during this vacation period. In the first two weeks after the strike, Amtrak had about a 5 percent to 10 increase in business, mostly on shorter hauls, such as in the Northeastern corridor. Extra equipment was added for about a week and then dropped when it turned out to be unneeded. Now, the spokesperson says, ridership is back down to about what would have been expected without the strike.

In the meantime, Amtrak telephones produced nothing but a busy signal for as many as 250,000 callers right after the strike started. The spokesperson said Amtrak reservations numbers are still sometimes hard to reach, partly because of the strike and partly because a new reservations system is being installed.