The National Symphony Orchestra, weary from more than 24 hours of travel, made a low-key arrival here Saturday night. Two kimono-clad young women waited with bouquets of roses and chrysanthemums for conductor Mstislav Rostropovich, and a Japanese official was there to offer a handshake that turned to his surprise, into a bear hug.

On the whole, there was more excitement a few yards away in the airport's foreign arrivals lobby, where a group of Japanese schoolgirls, all clad in neat uniforms with white berets, were being welcomed by their families on their return from an excursion. Rostropovich, suffering from fatigue and laryngitis, spent little time on formalities. After waiting to be sure all the members of his orchestra were safely through customs and the buses were there to take them to their hotel, he was taken off in a private car to attend a Russian Orthodox Easter service.

The scene had been livelier 24 hours earlier at Dulles Airport, where a trio sent by the musicians' union gave the orchestra a farewell concert. Reflecting the shortage of Japanese and Korean material in American popular music, the trio (Beets Johnson, clarinet; Doc Traupell, accordion, and Sammy Farrell, bass) gave their concert an Oriental flavor with such numbers as "Chinatown, My Chinatown" and "Slow Boat to China."

Then they dipped into the Russian repertoire, with a jazzed-up version of "Dark Eyes" played in honor of Rostropovich. The conductor was so touched by this gesture that he grabbed the nearest member of the orchestra, who happened to be veteran violinist Herbert Sokolov, and began jitterbugging wildly around the lobby. Several other couples were dancing more sedately, including the recently married double bass player Michael Ferrick and his wife. After the dance, Rostropovich said the concert "so touched my heart, I want to give you our first souvenirs from Japan," and he gave painted Easter eggs to the three musicians. Then he decided to give a wedding present to "our honeymoon couple."

"Here," he said, handling an alarm clock to Ferrick, "this is so you will get to rehearsals on time."

One of the 100-odd musicians who watched the concert admiringly from the sidelines was NSO tympanist Fred Begun. "Isn't that fun?" he said, nodding toward the trio from the musicians' union.

"I used to play with those guys a lot before I got my job with the symphony."

"The last time we did this," said union president Sam Jack Kaufman, "was in 1959, when they went to South America. We had a bigger group then, and they were all wearing sombreros. We thought of wearing Chinese costumes this time, but we weren't sure how it would be received."

It is possible to fit an entire symphony orchestra into a fraction of the space available on a 747, and the NSO members attracted little special attention as they filed to their seats on the Washington-to-Tokyo leg of a regularly scheduled Northwest Orient flight that began in New York and went on to Manila. The chief difference from an ordinary fight was probably that a lot of the passengers seemed to know one another.Little conversation groups of up to a half-dozen were scattered through the plane. Violist William Foster was taking a Japanese lesson from principal flutist Toshiko Kohno, a native of Japan, and there was a round-the-clock game of seven-card stud in the tail section. But on the whole, the musicians blended in harmoniously with the tourists and businessmen on the flight. "I hear we have a symphony orchestra on board," said a stewardess who had joined the flight in Chicago. "Which orchestra is it?"

The orchestra received V.I.P. treatment from Japanese customs, which checked only a small fraction of the groups's collective luggage, but not from Japanese airport security, which seems to be even tighter than at most American airports. Several members of the party, both male and female, were thoroughly patted down by security guards, and a number of pocket-knives (including that of Washington Star critic Theodore Libbey) were confiscated temporarily during the Tokyo-to-Osaka leg of the trip. "I'm glad to see them doing that," said one orchestra member. "I don't want any armed terrorists flying with me."

The first member of the party to get through customs in Osaka was NSO president Martin Feinstein, who strolled through nearly half an hour before any of the orchestra's members but then waited outside for the others to rejoin him. Did he use special influence? No, he explained, "I travel light."

In Feinstein's hands were a slim attache case and a small package of duty-free whiskey. At his feet was a compact suitcase, shaped to fit under an airplane seat, which looked like it might hold four loaves of bread. "That holds two suits, a tuxedo and a week's laundry," Feinstein said. "I never have to check any luggage -- I just carry it on, store it and, at the end of the flight, I can pick it up and walk out while everyone else is waiting in line."