Dulles International Airport, often called a "sleeping giant" positioned to become the East Coast's dominant airport because it has room to grow, must attract more passengers and overcome design pitfalls if it is to surge ahead of competitors, officials and industry spokesmen say.

Dulles has suffered stagnant passenger volume for the past three years, and it is largely dependent upon a single carrier in an industry rife with mergers and bankruptcy filings. The airport is run by an agency whose legal authority is in doubt, and the facility's potential for expansion is limited significantly by its design.

Yet boosters say Dulles could increase its passenger volume fourfold in the next several decades because of its ample 10,500-acre site.

"No other airport on the East Coast can be expanded the way Dulles can," said developer Bahman Batmanghelidj, who has several projects near the airport, which is in Fairfax and Loudoun counties.

Dulles opened in 1962 with a flood of optimistic predictions but only a trickle of passengers willing to drive nearly 30 miles from Washington. It grew slowly until the mid-1980s, when an era of deregulation and a booming economy sent ridership rocketing far past many projections. Just as suddenly, airport use sagged, and it has remained relatively flat for three years.

Meanwhile, ridership has increased steadily nationwide. Many officials attribute the Dulles slowdown to the withdrawal of Continental Airlines as United Airlines grew to dominate the airport with its hub of domestic flights.

Now, 3 1/2 years after the federal government handed control of Dulles and National airports to the independent Metropolitan Washington Airports Authority, local officials are taking a critical new look at the master plan for Dulles in an attempt to increase ridership and its stature among airports. The number of passengers who use Dulles this year may not equal the 1987 total of almost 11 million, officials say.

Whether the sleeping giant will stumble or storm into the 21st century will dramatically affect not only travelers' convenience, but also the region's economy. Estimates of the annual contribution of the airport to regional business surpass $1 billion and could multiply as ridership rises, particularly international traffic.

Airports authority officials play down the effect of a federal appeals court finding that part of the law giving the agency control of Dulles and National is unconstitutional. Even if the ruling stands on appeal, major decisions made now probably won't be overturned because the agency is acting in good faith and performing essential duties, the officials said.

But Patti Goldman, an attorney for the citizens group that filed the challenge, said individuals could challenge airports authority actions, and she predicted Congress will have to resolve the constitutional issue.

Among the keys to Dulles's growth is how well it is marketed to major airlines, whose increased commitments of service are essential to major construction projects. Airports authority officials say they want their long-term plans to include enough flexibility to change with the shifting needs of major air carriers. Yet they note that some decisions made in the next few years, such as the design of a costly people-mover system, may lock in many of the airport's features.

"We're significantly constrained as to how that facility can be developed," said authority member Ron Linton.

Some suggest that Dulles may have to play catch-up with other expanding airports. Dulles "is late to the party," said Clark Onstad, a former Continental Airlines and Federal Aviation Administration executive. "Other hubs on the East Coast were able to grow quicker" in the 1980s while Dulles was shifting from federal to local control, he said.

Onstad predicted passenger growth at Dulles will fall short of official projections for decades. Officials have started a $735 million renovation program at National, but they say its passenger volume is close to the maximum it can handle.

Among the airports with which Dulles will be competing for new routes -- particularly international flights -- is Baltimore-Washington International. BWI also plans to expand, but it has less than one-third the land that Dulles has and more modest growth projections.

Ironically, money is one of the smallest problems Dulles faces, despite the current budget crises for other major transportation services. The airports authority receives a steady stream of revenue from airlines, concessions and other sources.

A $480 million program of renovation and expansion is underway at Dulles, including the opening early next year of an international arrivals building. The length of the main terminal will be doubled in the next several years, and another $328 million worth of projects has been approved for late in this decade. The new Dulles could cost $3 billion over about five decades.

A series of midfield terminals and possibly a large terminal near the southern end of the property are envisioned as airline demand builds. The new facilities are to be linked by a people and baggage mover running in train tunnels blasted through thick diabase rock.

Construction and equipment for the first two 1,850-foot people-mover tunnels will cost more than $91 million, not counting all the expenses of the connecting station at the main terminal, officials say. The construction cost alone has been estimated at $13,400 per linear foot, and officials say it could be about 20 percent more if the system is elevated.

Two new runways are planned to supplement the three existing ones. Huge parking buildings are to be built. "We're talking about a humongously large airport" serving 55 million passengers a year -- as big as Chicago's O'Hare today -- if Dulles is fully built out, said airports authority General Manager James A. Wilding.

To fulfill the expansion goal, several design constraints at Dulles must be resolved. These include:

The main terminal. Officials agree the distinctive roof line, designed by Finnish architect Eero Saarinen, must be maintained as the building is expanded. In addition, no large structures should be built that would disturb the view of the terminal for passengers approaching the airport, consultants have advised the airports authority.

Transportation and parking. Parking spaces for up to 44,000 vehicles may be built, many at satellite locations linked to terminals by a shuttle system, adding to passenger inconvenience. Express bus and rail service extending from the Metro system to the airport have been proposed, but financial and planning hurdles remain.

The property. The configuration of runways and approach zones limits potential for terminal expansion and other development. One airports authority board member recently questioned whether a significant amount of additional land should be purchased for Dulles.

"Flexibility is absolutely essential," said Wilding. "We really don't know what direction aviation is going to go other than upward."