It has been eight years since they last played the U.S. Open on the hallowed grounds of the West Side Tennis Club in Forest Hills. The tournament had outgrown the old club in every way. The grass surface had been changed to clay. The stands and the grounds were cramped. It was uncomfortable for players, for fans, for everyone.

And yet there was the matter of tradition. Forest Hills was, after all, Forest Hills. The U.S. Tennis Association wanted to take an old bowl used for summer concerts and make it into a tennis palace, a place that would rank with Wimbledon and Roland Garros.

Foolish notion, said the purists. You can't just put up a net in the middle of LaGuardia Airport's takeoff and landing patterns and hold a major tennis championship. You can't locate yourself a couple of hundred yards from a baseball stadium -- a tacky one at that -- and create prestige and tradition.

The purists were wrong. In seven years, the U.S. Open at the National Tennis Center in Flushing has very much established its own traditions. On Tuesday, when the tournament begins its eighth year there, the planes again will be roaring overhead, usually on break point, but they are as much a part of the tournament's tradition as strawberries and cream are a part of Wimbledon's. Maybe the planes aren't as charming, but the strawberries and cream are overpriced.

At Stade Roland Garros in Paris, where the French Open is held, players talk about the red clay surface. They come off the court caked with it from head to foot and throw away their tennis outfits because the stuff simply won't come out.

Players at Wimbledon talk about the weather and the grass and the horrible transportation to and from downtown London.

In New York, players talk about the planes and the night matches and the adventure of working your way through the hordes to reach an outside court.

Perhaps it was Jimmy Connors, five times the Open champion and the No. 4 seed this year, who best summed up the world's three most important tennis tournaments.

"When you play in New York," said Connors, a favorite of the tennis audience here, "they come to see two guys kill each other. The crowd here knows I'll go out and spill my guts on the court to win and they love to see it.

"At the French, if you spill your guts, they just ignore it. And at Wimbledon, if you spill your guts, they'll ask you to clean them up."

What sets the Open apart from the other majors, including the Australian Open, is night play. The first 10 days of the tournament are divided into two sessions, one during daylight, one at night.

Players dread being scheduled for a night match. Not only does it mean waiting all day to play, it means a short night's rest after one does play. But every seeded player must play at night once before the semifinals.

Bjorn Borg never forgave the USTA for scheduling his 1979 quarterfinal with Roscoe Tanner at night. Tanner's 140-mph serve was blinding in daylight; at night, it was nearly invisible. Borg lost in four sets.

The next year, his night match was against Larry Stefanki. The USTA aims to please.

The night matches also affect fans. There are two distinct sets of fans at the Open. The day crowd includes the true tennis nuts. They wander the outside courts checking out new faces, looking for matches between unknowns who might someday be knowns. Often, they linger until dusk, watching one last doubles match on Court 16.

The night crowd is entirely different. Those fans come to see the stars -- John McEnroe and Ivan Lendl, Chris Evert Lloyd and Martina Navratilova. They wear suits and loafers, dresses and spiked heels. Or they wear expensive tennis sweaters. Since night matches are confined to the 20,000-seat stadium and the 7,000-seat grandstand court, they see much less tennis. But that doesn't matter. The next day, they tell their friends they saw Martina the night before.

Whom did she play? Who knows?

The most fascinating time is about 7 p.m., when the day and night crowds come together. The night people are arriving for a prematch meal, the day people are grabbing a bite before heading to the subway.

They come together in the concession area, the melting pot of the Open. Here, one can buy the world's most expensive and most delicious concession food. A hamburger is $5, but it is huge and terrific. Veal parmigiana goes for $9.50. Tables must be shared, so the kid in jeans eating a burger and soft drink often asks the man in the suit eating veal and sipping wine to pass him the salt.

There are other traditions. For instance, since the tournament moved from one end of Queens to the other, only McEnroe (four times) and Connors (three) have won the men's title. On the fast hard courts, U.S. left-handers seem to thrive. The women have had a little more variety, Evert winning three times, Tracy Austin twice and Navratilova the last two years.

The record, in short, is this: A U.S. citizen has won every singles title since the National Tennis Center was born. U.S. players complain their fans aren't chauvinistic enough. And yet, there appears to be a home court advantage.

If the new place has been a boon to U.S. players, it has been more than that to the USTA. Each year, crowds come in record numbers to a facility able to accommodate more than twice the number of fans Forest Hills could. A new TV contract with CBS that runs through 1990 is worth millions more.

Many players, seeing the USTA's riches, say there is a miserly quality to the organization. "People always talk about Wimbledon refusing to change," said veteran JoAnne Russell this summer. "But they have changed things; they have improved things for the players . . .

"But at the Open, it's a struggle to get them to change anything. Wimbledon gets a bad rap."

But Wimbledon is Wimbledon. The only plane that ventures anywhere near the All England Club is the Concorde. At the U.S. Open, the shuttle roars overhead all day.

And all night.