The National Capital Planning Commission has found crucial deficiencies in the long-range plans for the rapidly expanding Dulles International Airport and said the federal facility urgently needs better planning.

The influential panel, which is responsible for reviewing all development planned by federal agencies in the region, said the lack of planning endangered Dulles "just at the time the airport seems poised to fulfill the destiny foreseen at its inception."

"We are aware of the many pressures the FAA is under with the unprecedented growth at Dulles," the planning commission said in a letter to Transportation Secretary Elizabeth Hanford Dole. "Dulles, one of the most important gateways to the nation's capital, urgently needs overall master plan guidance."

An official of the Transportation Department, who asked not to be identified, said that the FAA had not yet received the letter. He said "most of the problems here involve money. We want better roads and we are aware that planning is crucial. But with no funds, it is tough."

Dulles, which emerged last year as the fastest-growing airport in the nation, is in the center of a booming technology belt on the border of Fairfax and Loudoun counties.

Congestion on the roads to the airport has grown along with the rapidly increasing use of Dulles, prompting concerns that Dulles eventually could become as overused and poorly planned as National Airport.

The commission sharply criticized the Federal Aviation Administration's failure to coordinate the growth of Dulles with the rapid development in the region it serves.

While the commission has advisory power and cannot order changes, its opinions play an important role in shaping federal development in the region. The commission said its advisory opinions have been rebuffed only once in the last 16 years when the U.S. Postal Service rejected the commission's recommendations last year and built a post office in Potomac.

The key problems at Dulles outlined by the commission were:

*The lack of a long-range plan for the airport to grow from its current level of 5.4 million annual passengers to its proposed capacity of 40 million.

*A need for improved forecasts for automobile traffic and the impact on the corridor surrounding the airport.

*The lack of a detailed analysis of the proposed widening of Rte. 28 and its impact on the airport property and surrounding development.

Hugh Riddle, deputy director of the Washington Metropolitan Airports, which oversees the management of Dulles and National for the FAA, said that he had not seen the letter and declined comment on its overall analysis.

"The commission basically feels that as each day passes, Dulles is losing a wonderful opportunity to plan for the future," Robert Gresham, an NCPC spokesman, said yesterday. "Good quality planning for Dulles is urgent and now is the time to do it."

A current Transportation Department plan to transfer the airports to a local authority -- which could float bonds to raise funds for development -- has passed the Senate and awaits action in the House.

Virginia's plans to widen Rte. 28, one of the main roads serving the Dulles area, to as many as eight lanes is a key to further growth in the area.

Virginia officials said this week that a new building plan for the state's Center for Innovative Technology near the airport could be hampered unless the center obtains access to Rte. 28. The NCPC recently told the FAA that the state's technology center could cause congestion on roads that would affect the airport.

In its letter yesterday, NCPC also said that Transportation Department officials had failed to take into consideration a possible reduction of passengers at National Airport and the increase in traffic that would bring to Dulles. National now serves about 14 million passengers a year, and can have no more than 16 million under current law.