When Washington Dulles International Airport opened in 1962, its planners, expecting millions of passengers to pass through the terminal each year, envisioned a huge surge of development in the sparsely settled land between the airport and the District of Columbia.

It took more than two decades, but activity at the airport, which once was viewed as an elegant white elephant, has begun to grow, and now development has increased markedly along the Dulles corridor. The corridor is defined as the land that runs along the Dulles Access Road and its companion toll road, and includes the meadows and forests to the south of the airport in the area bounded by Interstate 66 and Routes 50 and 28.

As more people live and work in the area, demand for and prices of real estate along the corridor have soared, particularly for the 5,000 acres of land that already have been zoned for commercial development.

"When the toll road opened up, it was pretty much like putting a freeway where none had existed before," said Thomas G. Morr, president of the Washington Dulles Task Force. "It made all the construction between the airport and Tysons Corner possible. The growth in that area has been profound by any measure."

Between 1960 and 1980, Fairfax County's population grew from just under 250,000 to almost 600,000, according to the county's Economic Development Authority. As the Dulles corridor attracts new residents and eager commercial operations -- mostly high-tech firms drawn to the region's highly educated work force and the ease of communication and travel -- real estate prices have marched steadily upward.

"What you are seeing in this county is a major boom," said Pat Hannum, an economist with the development authority. "Most of the land under contract and zoned for development is already in the hands of major developers."

Almost every week, a major firm decides either to move to the corridor or to develop some of the nearby land. TRW Defense Systems Groups, Electronic Data Systems, Satellite Business Systems, Verdix Corp. and AT&T already have committed themselves to placing operations in the area. Earlier this month, Fairfax developer Henry A. Long Co. and Perpetual American Bank announced plans for an elaborate $40 million conference center on 1,100 acres south of the airport. The resort-style center will be built by International Conference Resorts Inc., the nation's largest developer of conference centers.

Much of the growth 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 15 million square feet of that space along the Dulles Access Road. The amount of office space along the corridor is expected to double within the next 20 years.

Reston, the planned town that lies between Washington and the airport, is a barometer of the fast growth of commercial activity in the area. In 1979, commercial land was selling in Reston for $1.35 a square foot. The price rose to $2.75 by 1981, to $4 by last year, and to about $9 lately, according to Kenneth L. McVearry, vice president of Coldwell Banker Real Estate Services, one of the more active developers in the area.

The Dulles corridor became the obvious choice for the growth of high-tech firms in the Washington area as the Tysons Corner area became more urban in character, making office space far more expensive there for large businesses that have no retail needs, and increasing traffic in other areas along the Capital Beltway. Land at Tysons cost $2.50 a square foot in 1976, but the price had risen to about $50 by earlier this year, according to Fairfax officials.

"It all came together," said James Cleveland, president of Reston Land Corp., which is overseeing the development of Reston. "The promise of the toll road meant easy commuter access, and the airport responded to the growth in business with new flights. All this brings development and makes the area look more attractive to business searching for land."

Most of the work planned in the corridor involves major developers, who are building space for high-tech firms. The Metropolitan Washington Council of Governments estimates that more than 44,000 jobs will be created in the corridor between now and the year 2000.

A new study released by the Rice Center in Houston, which looked at the possibility of operating a privately funded rail line along the Dulles Access Road, estimated that, with an average need of 300 square feet of office space for each job created, total office inventory in the area can be expected to increase by more than 15 million square feet.

Most of that planned growth is already on the drawing boards of some of the area's larger developers. Some are building office parks speculatively, hoping to lease large quarters to companies for either permanent or temporary space. Others are taking parcels of land and attempting to turn them into huge parks for one or two tenants.

The Dulles Corridor in part is attracting new businesses because of the development of the Center for Innovative Technology, which straddles Fairfax and Loudoun counties.

Most developers, and the planning authorities in both counties, believe that the growth of high-tech business, with its relatively small demands on the environment and its heavy reliance on easy transportation and communication, will continue to play a major role in the population growth of the Washington area.

"Very few parts of the country are growing as fast or as coherently as we are in this region," said McVearry, the Coldwell Banker official. "What we are doing is creating a national marketplace with sophisticated developers and customers who know just what they want. The match is perfect."