The National Capital Planning Commission said a commission lawyer quoted in yesterday's Metro section overstated the agency's authority to block highway access to the Center for Innovative Technology in Northern Virginia. The commission's decisions generally carry considerable weight, but are advisory.

When Xerox Corp. came to Loudoun County in 1974 to establish its International Training Center, company officials were transfixed by the area's vast beauty and delighted by the proximity of Dulles International Airport.

Their joy soon turned to helplessness, though, as airlines ignored America's first jetport. Although it was billed as the airport of tomorrow, flights to Dulles were so few that for years Xerox was forced to rely on National Airport, busing thousands of people to the center.

"Sometimes it is hard to believe what has happened here," said Bob Sohl, director of the Xerox Center, which now flies more than 10,000 people into Dulles each year. "The importance of the airport cannot be overstated. It is the absolute backbone for growth in the region."

The emergence last year of Dulles as the fastest-growing airport in the nation, and the steady migration of educated workers into surrounding Fairfax, Loudoun and Montgomery counties, have fueled a potent high-technology explosion that experts say will transform the Washington metropolitan region by the year 2000.

Dulles, which lay moribund for 20 years, has played an increasingly visible role as the area's focus shifts from just a federal city to a new Silicon Valley. Air service has grown by more than 200 percent since 1981, and this new access to dozens of American cities has drawn an almost weekly procession of corporations to the suburban area.

Hundreds of firms, including TRW Defense Systems Groups, Electronic Data Systems and AT&T, have moved to or committed themselves to major new developments in the area. The state's new Center for Innovative Technology on the border of Fairfax and Loudoun counties has helped encourage the boom.

This week, George Washington University announced that it will build a major instructional and research center on part of a 576-acre tract near the Loudoun-Fairfax county line that will be developed as a research and development park.

The Dulles area is generally recognized as the land along the Dulles Access and Toll roads, the meadows and forests to the south of the airport and the property bounded by I-66 and Rtes. 50 and 28, but is beginning to extend into Loudoun County.

More than 80 percent of all nonresidential construction now approved or under way in the Washington area -- worth more than $4 billion -- is in the immediate corridor served by the airport, according to the Washington Dulles Task Force, a private nonprofit organization that promotes the growth of the airport. Industrial and commercial development of the corridor was always part of Fairfax County's plan but during the past two years the rate of development has far surpassed even the rosiest predictions.

Although the growth of Dulles has been remarkable -- 5.4 million passengers passed through its sloping glass terminal in 1985 and the number of users has risen for 52 consecutive months -- success has been a long time coming.

Deregulation of the airline industry in 1978 hurt Dulles badly, as carriers fled the underused facility for more profitable and densely populated locations. In 1981 the airport had only 2.1 million commercial passengers.

"It's almost astounding to think back a couple of years and realize that Dulles had no air service to New York, Chicago or Boston," said James A. Wilding, director of the Metropolitan Washington Airports, which operates Dulles and National for the Federal Aviation Administration. "I am thoroughly persuaded that the growth of the airport and the boom in high-technology industry are completely related. And I think it is something that could continue for the rest of the century."

By 1985, with the local population growing almost 40 percent each year, transportation analysts and local officials say that Dulles turned the corner for good.

Five airlines announced in 1985 that they would established hubs -- a base of operations -- at Dulles: New York Air, Pan American, Presidential Airways, Air Wisconsin and United Airlines. Together, they account for almost 200 departures each day, and have pumped millions of dollars into the local economy.

Last fall, Presidential set up a home base at Dulles, and Harold J. Pareti, former president of People Express, hopes that his new carrier will help do for Dulles what People did for Newark International Airport.

"When we first organized the airline, we had the vision that Dulles was going to become one of the major business centers in the United States," said Pareti. "That is exactly what we are seeing. The companies are just flooding into this area and Dulles airport is at the hub of all the activity."

But Dulles' biggest plum came in December, when United, the nation's largest carrier, announced that it will establish a major East Coast hub there in May. The airline will offer 50 flights a day at first and expand during the next two years.

"We wanted to open our markets in the East and we took a hard look at what made sense," said Christopher Bowers, senior marketing manager at United. "The more we looked at Dulles, Virginia and the Washington market, the more excited we got."

Demographic trends in the Washington area explain much of that excitement, showing a significant westward shift of the population, income and employment that is expected to continue for years.

According to census statistics and Washington area planning officials, the Washington area is the only northeastern metropolis projected to exceed the national average in population growth through the year 2000, and much of that growth is expected to occur in the area west of the Capital Beltway, near Dulles.

That's particularly good news for Dulles, because service and high-technology industries, and their employes, require more frequent travel than most professions. A recent study by the Bureau of Economic Analysis says the Washington area now is second only to San Fransisco in per capita income levels -- a key indicator of flight demand -- and that if the Dulles corridor were taken alone, it would be first.

Finally, during the past decade more than 80 percent of the metropolitan area's growth in employment took place near the airport, according to Fairfax and Loudoun county population statistics -- another trend that is expected to intensify.

"If you look at the numbers, we belong in the Sun Belt," said Thomas G. Morr, president of the Washington Dulles Task Force. "The change has really been eye-popping."

Much of the growth in the area has been sudden. In the past six years, office space in Fairfax County has increased from 10.4 million square feet to about 36.5 million square feet, with about a third of it lining the Dulles Access Road.

The corridor was a natural home for high-tech firms that found prices at Tysons Corner too expensive.

And with almost all the major parcels of land in Fairfax already in the hands of developers, businesses are turning more frequently to Loudoun, a county once thought of as a bucolic outpost.

In the past year, 79 companies, most of them medium-sized industries, moved to Loudoun, according to the county Economic Development Office. That figure was double the previous year's. The value of nonresidential construction almost tripled to $51 million, according to June Bachtell, director of economic development. Bachtell said the airport's accessibility, and the relative quiet of the county, were essential in luring new firms there.

"The Beltway is expensive, congested and unpleasant," said Bettie Kennedy, director of industrial relations for Magnavox, which moved its systems engineering division to a shimmering glass building in Loudoun last fall. "We need the flexibility to come and go, we travel all the time."

Kennedy said her employes were drawn to Loudoun because they could choose among widely different life styles. "If they want a farm with 10 acres, they can have it. If they want a high-rise in Fairfax, they can have that, too."

But rapid growth has its drawbacks. Congestion increases every day on the roads in Northern Virginia, and most workers who have been there for a while say that if a solution is not found soon, bottlenecks will threaten the region. The Dulles Airport Access Road, a 16-mile highway connecting I-66 and the airport, is largely restricted to airport traffic. A toll road that opened the route to local traffic was completed in 1984, but traffic has been far greater than expected.

There is a rail link to the airport from West Falls Church, where a Metro station will open in June, but Metro has no funds to develop it. A private organization, Dulles Area Rapid Transit, has proposed building a privately funded high-speed rail on the line. But local opposition to mass transit spending will be a difficult hurdle for the company.

And the airport that so long suffered an image as a slumbering giant is now threatened by its own rapid growth. The FAA, which operates Dulles, says that the airport can tolerate unabated growth until the yearly passenger level hits 8 million.

That, however, could happen this year. And although most American airports are owned by municipal authorities that pay for improvements by floating bonds, that is an option not available to Dulles.

Because it is owned by the federal government, the airport has to draw its funds from the U.S. Treasury. Budget cutters have not been kind to Dulles and National and both are in need of several hundred million dollars worth of work.

At Dulles, it is likely the money would go first to a new midfield terminal and the expansion of the main building. A federal plan to transfer the two airports to a regional authority is awaiting a Senate vote, and if it passes, must go to the House.

"All we need is the planning to work out," said Morr. "We are so fortunate to have both the airports in the area, it's an advantage few cities have these days. After years of begging people to take Northern Virginia seriously, I would hate to see people scared away by the crowds."