A splash of red wool and blond hair against the silver of an airplane's hull, Diana, princess of Wales, arrived at Andrews Air Force Base yesterday, Prince Charles by her side and the air filled with cheers and cries of "Princess! Princess!"

Within 20 minutes, the couple was gone, on their way by helicopter to a day filled with a White House welcoming ceremony, official visits around the city, an off-the-record press reception and a White House dinner studded with guests such as dancer Mikhail Baryshnikov, physician Jonas Salk and actor Clint Eastwood.

The three-day visit was designed as an opportunity for the couple to see the National Gallery of Art's "The Treasure Houses of Britain" exhibit, a glittering celebration of the English country house; Charles and Diana are the official patrons. But during the months of preparation, anticipation, hoopla and hype that preceded the trip, Diana's first to the United States, it became clear that for the Americans, these three days had ramifications beyond any visit to an art show.

"Basically, Americans have always wished in some ways -- not in all ways -- that they had a royal family and that they had some titles because it sounds like fun," said Pamela Brown, wife of National Gallery Director J. Carter Brown. "I'm not sure they really want it, and I'm not sure we should have it, but it has a certain magic."

At Andrews, the personifications of that magic made their way down the edge of the crowd, estimated at 4,000, shaking hands and smiling into the throng. Union Jacks provided by the British Embassy waved and children threw their arms around Diana, who received presents ranging from flowers to puppets labeled "Prince William" and "Prince Harry."

Ann Waymire, 15, and her parents rose at 4 a.m. to get from Springfield to Andrews early enough to be the first in line.

"This is happiness, right here on these girls' faces," said Geraldine Waymire about her daughter Ann and 15-year-old Laura Barchi, who managed to press a bouquet of flowers from her garden into the princess' hand.

Crowds trailed the couple throughout the day, 1,000 waiting for the prince outside the American Institute of Architects, where he attended a discussion of urban renewal, and 2,000 greeting Diana and Barbara Bush at the Washington Home and Hospice.

In the weeks preceding the visit, social Washington was thrown into an unusually public frenzy when it became clear that the few parties Charles and Diana were to attend would be small and the guest lists impervious to influence or persuasion.

The fever was heightened by last week's arrival in Washington of more than 150 British lenders to the "Treasure Houses." Ferried through a round of parties in honor of the show, the members of the British nobility became prized trophies for both the hosts and hostesses of Washington and an American press suddenly seized with Anglomania.

Diana, who garnered more attention than her husband, appeared on the covers of Time, Newsweek, People, Vanity Fair, Life, Ladies Home Journal and TV Guide -- not to mention the daily press. Network television documented the fuss on morning and evening news shows. ABC purchased a British television interview with the couple for broadcast last week on its "20/20."

Columnists waxed philosophic about the decline of the British Empire and America's yearning for aristocracy.

About 150 members of the British press are here to cover the visit, and more than 400 of their American counterparts are expected to trail the couple at every stop. At Andrews, the horde of reporters and photographers swooped down on each dazzled child who had shaken hands with Diana as if checking out the results of contact with King Midas.

For all the commotion, relatively few will actually be able to see Charles and Diana. A total of about 1,500 will attend the small, private events where there is any hope of socializing with the royal couple. Another 2,000 can be seated at the Washington Cathedral today for services the prince and princess will attend. Royalty-watchers were planning to arrive as early as 5:30 a.m. to get in line for admission at 9.

The visit and gallery exhibit are being trumpeted as celebrations of Britain, its country homes filled with riches and history and its royal family surrounded by wealth and glamor. It is also a celebration of public relations.

Entrepreneurs are making the most of the events. Life-size photos of the Waleses have sprung up in downtown Washington for anyone who would like a picture taken next to the cutout figures. A large and glossy picture of Charles and Diana and a message of welcome grace a window of Garfinckel's at F and 14th streets, and at least one local hotel will be serving such British favorites as steak and kidney pie and trifle for the duration of the exhibit.

"We won't know how much it costs until all the bills come in," said Jerry terHorst, corporate spokesman for Ford Motor Co., which is underwriting the exhibit. The company won't be specific about the extent of the financial commitment, its largest ever to a cultural event, but Ford's contribution is expected to reach $3 million. The company paid for such things as the catalogue, exhibit installation, advertising, a party for the British lenders to the show and Monday night's dinner and reception at the gallery.

Ford decided to sponsor the exhibition in May 1984, long before the royal visit was announced on March 21. TerHorst described the visit as "the frosting on the cake." Without the royal couple, coverage of the exhibit might have ended with the show's opening last Sunday.

Some beneficiaries of the publicity surrounding the visit are frustrated by the focus of the coverage and enthusiasm.

"Everyone is paying a lot of attention to the social side of things," said Mary Means, director of the American Institute of Architects Foundation, who described the session there as one of the visit's few substantive events. "This is what should be paid attention to, but I'm not sure that with all the glitter of royal-watching it will be."

There are some dissenters, however, including a number of Irish American organizations that plan to stage protests during the visit. Several hundred protestors chanted "IRA, All the Way" outside the White House last night.

"To Americans now, the royal family is a symbol of some fantasy world and something quite romantic," said Father Sean McManus, national director of the Irish National Caucus, an Irish lobbying organization. "But in reality, to a person from Northern Ireland, the British crown is the personification and symbol of repression, institutionalized violence, state-sponsored terrorism."

But as the couple's first day in the United States progressed, the prevailing spirit was one of adulation.

"I curtsied," said Susan Dillenbeck, 25, after meeting Diana at Andrews. Dillenbeck traveled from Chicago just for the visit and plans to see Diana at every public event.

"I just died."