The crowds begin to descend on Rayfield Barber only minutes after he takes his post on the curb in front of National Airport's main terminal each morning at 6:30. The rush keeps up for three hours.

Barber, 70, a skycap, goes into his double-time routine, hauling suitcases out of car trunks, laying them on his handcart, and threading his way through the crowds to deposit his travelers at the correct ticket counter. "You've got to hustle," said Barber, who makes most of his money from tips.

The pace wasn't always so frantic. Barber, who carried bags for the airport's first passengers the night it opened -- June 16, 1941 -- remembers a quiet place that was home to small DC3s with propellers, across the river from a sleepy Southern city. He remembers President Franklin D. Roosevelt's unannounced visits to the airport on warm summer nights and swanky Big Band dances in the terminal's upstairs lounge.

Now the piped-in music in National's terminals is punctuated by the roaring backbeat of jets taking off and landing, one almost every 30 seconds. The airport, one of the nation's busiest in number of flights per square feet of space, is jammed with people from 7 a.m. to 10 p.m.

Except for the construction of a few terminal buildings over the years, the airport has changed little since that night in 1941. Aviation executives, area residents and even its owner, the Federal Aviation Administration, agree the airport's roadways, curbs, sidewalks, ramps and waiting areas are not equipped to deal with the 14.6 million persons who use it every year.

The crunch is worst in the mornings, around noon, and in the evenings, the rush hours for modern airports when waves of people sweep through the place and then are gone. Few of the rushing passengers pay much attention to the aging terminal or the people who make it work.

For passengers, National is a means to an end. For the 7,700 people who earn their living there without taking off the ground, it is a series of individual worlds, separate and yet moving to the same rhythms, somehow combining for the larger purpose of getting people where they want to go. Whatever the job, it is affected by the daily cadence of airport life, the three-times-a-day lunge to move the paying customers from here to there. The men and women who work at National have a name for the frenzy. They call it "the Chinese fire drill."

Manning his post on the curb in front of the airport's main terminal, Robert J. Murphy is on the front line of one of the most congested roadway systems in the Washington area.

As an FAA policeman, he sees the traffic jams and the wide-eyed pedestrians with luggage sprinting across lanes of oncoming traffic, and he hears the screeching brakes and honking horns. These are people, said Murphy, who are near the edge.

"Women and all curse you out, well-dressed men lose their temper, getting red in the face," said Murphy, scanning the early evening traffic pandemonium outside the TWA terminal. "People want to get into that terminal and to hell with everybody else."

Murphy recalls one man in a business suit who became so frustrated waiting to get into a packed parking lot near the terminal that, when a police officer told him to move on, he wordlessly rammed his car into the lot's electronic gate.

"It's like a war here," Murphy said. "You can be a nice guy and it backfires on you."

"People ask me, 'How do you handle this job?' We say, 'At 10 p.m., it'll all be over with.' " Baggage Handler

For Ron Willis, the name of the game is "turnaround."

That's the amount of time needed to unload and service a plane before it takes off again. For Willis, a baggage handler for USAir, cutting "turnaround" is everything.

USAir officials pride themselves that their turnaround time at National -- which involves removing passengers, cargo and garbage, then reloading the plane with passengers, cargo and food -- is about a half-hour. The average time between a plane's arrival and when a passenger picks up his suitcase at the baggage claim area is nine minutes, a minute less than some competitors.

"We shoot to get them in and out as fast as we can," said Willis, who supervises a shift of 25 men loading and unloading about 115,000 pounds of luggage, mail and freight each day at the airport. "We say, 'speed and no damage.' "

Among his talents, Willis has become a connoisseur of luggage locks in his 24 years on the job. A broken suitcase lock, and the sight of a suitcase full of shirts and underwear blowing away down the tarmac, are a baggage man's nightmare.

"Any little jar will knock this open," said Willis as he dropped a blue Samsonite just taken off a flight from Albany. The lock popped open. "It's a suggestion. If they have a weak lock, put a belt around it."

"We move fast, efficiently," Willis said. "With all of the running around, we may look disorganized, but we're not. We're doing a job." Company President ar from the sound of crashing luggage, is a low-slung gray cinderblock building known as Hangar 12.

Looks are deceiving at National Airport. This is the international headquarters of one of the nation's biggest airlines, USAir, a Fortune 500 company that had revenues of $1.4 billion last year. Inside are the offices of Edwin I. Colodny, USAir's $500,000-a-year chairman and president.

Colodny, whose airline has 1,000 flights a day and flies 16 million passengers a year, is known in the airline industry as a no-frills pragmatist, and the office decor resembles the accounting department of a VA hospital.

"It's down-scale; understated is an understatement. It's functional," Colodny said. "Having a fancy office does nothing to generate revenues."

Colodny is legendary within his company as a stickler for detail and one who tries to see his business from the passenger's point of view. He had the flight attendants' uniforms redesigned in the 1970s, making them the first of any airline to wear hot pants (that practice ended two years later). He chose the company's name when it changed from Allegheny Airlines in 1979.

Under his leadership in this era of airline deregulation, USAir has flourished while other airlines have lost money or gone bankrupt. Colodny believes it is a result of the simple lessons he learned busing trays in the Adirondacks in his youth. "You have to pay attention to the details." Caterer------

The chicken kiev, rice pilaf and green beans almondine move so rapidly off the assembly lines at Marriott Corp.'s cavernous hangar that the women wearing white hats can barely keep up. They catch the trays, line them up on giant carts and wheel them one after another into cold rooms the size of gymnasiums.

Bob Mostert, chief of Marriott's airplane food preparation division, watches the movement of food from three video terminals on his desk, flipping dials to make sure work is moving apace.

"The main consideration in this business is being on time; don't delay that aircraft," said Mostert, whose 230 workers prepare 8,000 "in-flight" meals a day for travelers out of National.

Workers at the rows of conveyor belts are on the job 24 hours a day, placing cups, saucers, silverware and other items on fast-moving trays, and cracking eggs, ripping lettuce and squirting sauces. They prepare all the snacks and meals for 10 airlines flying out of National.

Each week, workers there use 25,000 dinner rolls, 9,700 eggs, 10,000 cups of milk, 8,800 tomatoes, and 9,700 chickens. Marriott has similar operations at 50 airports around the United States, but being in Washington sometimes presents special problems.

Of all his assignments, Mostert said, catering Democratic presidential candidate Walter F. Mondale's two planeloads of staff members and reporters is one of the craziest.

A major complication is that Mondale doesn't eat red meat. In addition, the Marriott staff doesn't know until just hours before Mondale's takeoff where he'll be going or how many they'll have to feed his entourage can vary from 60 persons to 250 . His staff often changes the plane's entire dinner menu three times in the hours before takeoff because of the whims of Mondale's aides and reporters, considered the pickiest and most voracious eaters, Mostert said.

"This business calls for some quick decision-making," said Mostert. "We have to really scamper." Weatherman

Mark Richards is loping around his office again, taking readings from his wall full of electronic dials, scribbling quickly in notebooks. "This is quite hectic," he said. "Weather has always been a thankless job."

Richards is a weatherman at the National Weather Service's observatory on a terminal roof. From its small warren of offices there, the weather service churns out weather data for federal agencies, the news media and the telephone company's hourly weather announcements.

Only one weatherman works at a time at the National station, and the job can be frantic, what with the constant checking of ceilometers, altimeters and gust recorders, and the required jottings in charts and graphs.

On one recent day, a cold front from the west was bringing a 6,000-foot cloud cover, intermittent showers and a sense of urgency. "The worse the weather, the harder we work," said Richards, who speaks in rapid-fire bursts, in part because he often can't find much time between each task.

Richards said the job sometimes seems strange because, as hard as he works, he doesn't deal with coworkers or the public. Because of the volume of work, the office is off-limits to visitors, and workers keep its phone number even from most fellow federal agencies.

Richards said the best thing about the job is setting temperature records, but he acknowledges that pleasure was clouded somewhat two years ago when the weather service discovered its thermometer on the runway was out of whack, running two degrees warmer than it should have. The discovery called into question several temperature records over 100 degrees in the summer of 1980.

Richards, perhaps reflecting the whim of the heavens that he studies, adds, "It's very up-and-down." Skycap------------

When Rayfield Barber began working at National, he was grateful for his $15-a-week job, which was nine hours a day, six days a week.

In his first 17 years there, skycaps were not provided with carts, but had to hand-carry all bags, up to six at a time.

Blacks were mostly restricted then to jobs as skycaps and janitors, and black travelers could not eat at the airport restaurants. It was not until the late 1940s that the NAACP succeeded in integrating the airport restaurants.

"When all these changes took place, we'd feel good about it, but we couldn't let our feelings be seen," Barber said. "Keep your mouth shut. That's survival."

In recent years the airport has boomed, but Barber said he still makes only $2.01 an hour in wages from the skycap company, has no pension, and can't afford to quit.

"I've worked all my life," he said. "If you want to make it, you've got to hustle."