National Airport would become noisier and more congested under proposed U.S. Senate legislation allowing more daytime airline flights there, local officials and residents say.

The bill, which would remove federal limits on the number of airline flights per hour at National and three other busy airports in New York and Chicago, also would reignite debate over National's future by breaking recent congressional promises to limit traffic at the airport, local officials said.

The proposal would have a "very extremely damaging impact on the residential areas around National Airport," said Alexandria Mayor James P. Moran Jr.

Moran and D.C. Council member Betty Ann Kane (D-At Large), chairwoman of the Metropolitan Washington Council of Governments Committee on Airport Noise, said they had asked to testify in opposition to the bill at a hearing today of the Senate subcommittee on aviation, but were rebuffed.

Senate sponsors of the bill said it would increase airline competition, add service and reduce fares for travelers by allowing more commercial flights at National, New York City's LaGuardia and Kennedy International airports and at Chicago's O'Hare Airport.

Members of Congress frequently have become involved in issues on National Airport, eager to protect flights to their home states. The current legislation is sponsored by Sen. John McCain (R-Ariz.). One of the airlines eager to get a bigger share of the Washington and New York markets is America West, with headquarters in Phoenix.

Since 1969, the Federal Aviation Administration has limited the number of scheduled passenger jet flights at the four heavily used airports to prevent excessive delays. The limits have changed over the years and now vary from 37 flights per hour at National to an average of 120 per hour at O'Hare.

The FAA allocated landing rights among the airlines using the airports, and allows the carriers to buy and sell these "slots." That policy has triggered complaints from carriers that have wanted to start service to those airports but found no slots for sale, or faced prices of more than $1 million a slot.

"Slots harm free competition in a deregulated airline industry," said McCain. "Passengers pay higher fares nationwide as a result."

McCain's bill, supported by the airline industry, would eliminate the slot limits over 18 months, and during that time would add more slots for new entrants and prohibit airlines from buying and selling slots.

Local activists against airport noise oppose the bill. The limit on flights "is absolutely critical both for safety and environmental concerns," said Sherwin Landfield, spokesman for Citizens for the Abatement of Airport Noise.

The Metropolitan Washington Airports Authority opposes the removal of the limit on flights at National because that would "reignite the debate over the future" of the airport, said general manager James A. Wilding, in a letter to the subcommittee.

The flight limit at National has been "embraced by all concerned as a key device to control groundside congestion, inadequate terminal capacity, and aircraft noise impact on residential areas," Wilding said.

O'Hare officials said they welcome elimination of the limits on flights. Officials at LaGuardia and Kennedy said they cannot handle more traffic at peak periods and would consider imposing their own limits if the federal limits were abolished.