Airport officials are starting the new year with a campaign to win support for plans to transform National Airport from a dilapidated, dysfunctional traveler's nightmare into their vision of a transportation dream.

Under the $400 million proposal, which already has attracted opponents, many of the outdated and cramped airport buildings and roads would be replaced with more spacious facilities that planners say would emphasize passenger convenience.

Travelers would enter the airport on a double-decked roadway to find a new three-story steel-and-glass terminal next to the Metro station, three new parking garages with spaces for 5,500 cars and a two-story taxicab holding area with room for 800 cabs.

"I think it's great," said Linwood Holton, chairman of the board of the Metropolitan Washington Airports Authority, which operates National and Dulles International airports. "This will enable us to take care of the passengers using {National} right now . . . while not denying that there will be a few more passengers."

About 15.7 million passengers a year struggle through National, which has been expanded haphazardly since it opened in 1941. Airport planners expect to see 19 million a year by 2005.

Critics of the plan argue that the authority should find ways to reduce airport use and thus airplane noise, rather than accommodate growth.

Under the plan, the total number of jet aircraft gates would remain unchanged at 44; the number of jet takeoffs and landings is limited to 37 an hour by law. Therefore, planners say, critics are wrong to label the plan an expansion.

"We just want to make passengers more comfortable," said Saul Jacobs, project manager for Howard Needles Tammen & Bergendoff, the design firm working with the airport authority.

However, the number of passengers using National is expected to grow if the Federal Aviation Administration allows airlines to bring in larger jets. The airport plans anticipate a terminal capable of handling bigger planes.

The proposed new terminal "would be a huge and costly white elephant," according to a report by Citizens for the Abatement of Airport Noise Inc.

Authority board members are reviewing the proposal and hope to decide this month whether to adopt it as a master plan to guide construction at the airport in the next five to seven years.

The need for improvements at National has long been apparent to harried travelers frustrated by clogged and incoherent roads, full parking lots and lines of travelers blocking narrow passageways, waiting areas with few seats, overwhelmed baggage carousels, pint-sized concession and refreshment areas and tiny rest rooms.

Anyone who has lugged baggage across four lanes of traffic and over the three-quarters of a mile from the Metro station to the main terminal will appreciate the planners' proposal to shorten that distance.

The plan places a new main terminal, close to the Metro station, on land now occupied by a parking lot and the North Terminal used by Delta Air Lines and Pan American World Airways.

The new terminal would lie 170 feet away from the elevated Metro station, less than half the current 400-foot walk from Metro to the North Terminal. A pedestrian walkway over the two-level roadway would connect Metro with the third floor of the terminal and would open into a glass-walled area offering an expansive view of the runways and the Potomac River beyond.

"We hope the plan will encourage more Metro use," said Jacobs.

The old main terminal, which is registered as a historic structure, would be restored. The number of passengers using it would be reduced by shifting most of the gates handling large jets to the new terminal.

The number of large aircraft gates at the main terminal would be reduced from 33 to 12, and 10 gates would be reassigned to smaller commuter aircraft.The new terminal would have gates for 32 jets, and 1,00 feet of curb space on each of three road levels -- the ground for airport service vehicles, the second for arriving passengers and the third for departing passengers.

The antinoise group would like to see National rebuilt as a "small jewel," handling perhaps half as many airplanes and passengers, said Peter Engelmann, chairman of the antinoise group's Planning and Technical Committee.

The group is urging the authority to consider cutting air traffic by building terminals with as few as 20 gates for jet aircraft, less than half as many as now.

"Do you really think you can turn the clock back?" asked Polly Shackleton, a board member from the District, at a meeting with antinoise group representatives last month. "It seems so unrealistic,"

"My feeling is that we have to take care of 18 million passengers" a year, Holton said.

Airport noise was the major concern expressed after the plan was outlined Tuesday night to Arlington residents, at the latest in a series of public meetings.

Airport and airline officials say that the construction plan will not affect airplane noise. "It is not the number of people, it's the number of planes that makes noise," said James T. Murphy, a vice president of the Air Transport Association, an airline industry group.

The newer and larger aircraft are quieter than many planes now in use, including the ubiquitous Boeing 727 and early versions of the McDonnell Douglas DC9. The quieter planes can be used at the airport between 10 p.m. and 7 a.m., when noise rules prohibit takeoffs and landings by older jetliners.

The airlines endorse the proposed renovation because National "is just totally inadequate," Murphy said. "For many, many years, National has forced people through an obstacle course, and that is not the right way to treat people."

National earned its reputation as an ordeal to use and eyesore to view during the years when the growth in passengers outstripped Congress' willingness to pay for improvements.

The airport authority was created to finance and oversee operations and construction at both National and Dulles. The FAA turned over control of the airports last June, and the authority directors have voted to break ground this spring on the first $100 million in improvements.