The committee planning National Airport's future nixed a costly relocation of the airport's planned terminal yesterday, saying that a new control tower would solve a vexing design problem and save millions.

The decision by the Metropolitan Washington Airports Authority's planning committee came a week after the panel learned it could cost $100 million to shift the terminal site to correct original plans that would have had the terminal blocking the control tower's view of part of a runway.

"I think all this leads up to moving the tower," said Linwood Holton Jr., chairman of the authority's board of directors. Holton said the additional expense, coupled with architects' estimates that moving the $200 million terminal would delay the project two to three years past its scheduled completion in 1994, made it "a plan we just weren't willing to accept."

Airport authority staff members say they are not sure how much a new tower would cost, but estimates are that it could add $15 million to $20 million to National's $735 million renovation program.

James A. Wilding, the authority's general manager, said yesterday's decision means that several projects near the planned terminal, including three parking garages and a two-level road, will not be delayed. He said several sites are under consideration for a new tower, one of them atop a parking garage planned across from the new terminal, another on the opposite side of the airport, between the runways and the Potomac River.

"If we decide on a tower plan soon, I don't think we would be looking at much of a delay" in National's renovation program, Wilding said.

Raising the existing control tower is still a possibility, staff and board members said, but doing construction around working air traffic controllers would be complicated.

Under the airport's master plan, one of the new terminal's three arms would have blocked the control tower's view of the northern end of Runway 15-33, a 5,189-foot strip used primarily by commuter and private aircraft. Several board members said they were not aware of the flaw until recently.

Wilding and his staff, who have known about the problem for two years, have said they believed it could be solved by merely repositioning or shortening the northern arm of the new terminal.

Board members expressed disdain for that idea because it would mean ceilings in two of the terminal's three arms would be well below the 17-foot height deemed desirable by the terminal's architects. And airlines, which have urged the authority to build a new tower to solve the problem, have been cool to proposals to change the configuration of the new terminal's 35 gates.

"I don't want to sit here for the next 50 years and hear complaints from airlines" whose gates would be moved if the terminal's northern arm were refigured, Holton said yesterday.

Holton said that until the last few days, he had considered construction of a new control tower as a last resort to solving the design problem.

"The general manager told me that that was the last option we ought to look at, and I believed him," Holton said.

Wilding, who had warned board members that building a new tower could require a long approval process by the Federal Aviation Administration, said yesterday that he should have given more consideration to a new control tower.

"I probably went by that option too fast," Wilding said. "It was my idea that {the design flaw} was easily solvable, and that turned out not to be the case."

A group representing airlines at National praised the board's move toward a new control tower.

"We agree with what they've done in concept," said Dick DeiTos, executive director of the Metropolitan Washington Airports Committee, which called this week for a new tower. "The one outstanding item is how much this is going to cost."

The National Capital Planning Commission, the planning agency for the federal government in the Washington area, is likely to join the authority and the Federal Aviation Administration in discussions concerning a new tower.

The commission, which on several occasions has expressed concern about proposals for tall construction projects that would affect views of the Mall area, will not comment until actual plans for a new tower are submitted to it, spokesman Lee Feldman said yesterday.

Although they rejected moving the terminal west to be adjacent to the Metro station, airport authority board members told architects yesterday to design the pedestrian bridges that will link the terminal with the station so that Metro riders will feel they are in a part of the terminal when they get off the train.

"There were some very attractive features" in the relocation plan, board member Ron M. Linton said. "We'll end up with a better terminal in the long run, having gone through all this."