Airport officials and anti-noise groups, often adversaries on issues involving National Airport, are joining forces as Congress considers proposals many fear would add to the congestion and noise at the busy facility.

The unusual alliance is partly in response to a Senate bill that would create a federal noise policy. Long a goal of airlines frustrated by varying restrictions among U.S. airports, a nationwide policy is anathema to local officials loath to surrender control of noise policies to the federal government.

Airport officials also say that the bill, sponsored by Sen. Wendell H. Ford (D-Ky.), would create chaos at National by allowing more daytime flights.

James A. Wilding, general manager of the area airport authority, said the bill's plan to eliminate federal limits on the number of flights per hour at National could make obsolete the airport's $735 million renovation program, which airport officials approved with the understanding that Congress would not move to increase traffic there.

Meanwhile, a House subcommittee began hearings this week aimed at legislating a federal noise policy, another signal that liability questions and other concerns that have stymied such efforts for years are being overshadowed by calls from airlines and communities alike for noise guidelines.

Ford's proposal is not expected to make it out of Congress this session, and a noise policy proposal will not be introduced in the House until next year. But local airport officials and anti-noise groups say the moves toward federal policy changes that could dramatically affect National has put them on alert.

"What's being talked about now says to airport operators, 'You guys go mind your parking lots,' " Wilding said. "We don't want to see something that would interfere with localities' ability to set noise limits."

Although Wilding and other airport officials support the idea of a federal noise policy, they object to the plan outlined in the bill because it is not as strict as National's existing noise policy, which calls for a phase-out of older, noisier aircraft such as the Boeing 727 by 1998.

National's noise policy, one of the most restrictive in the country, also limits flights between 10 p.m. and 7 a.m. to newer, quieter aircraft such as the Boeing 757.

For anti-noise groups who pushed airport officials this year to limit noise at National even further, the possibility of local policies being undermined by less restrictive federal law is alarming.

"People here have put a lot of effort into what we have," said Arlington County Board member Mary Margaret Whipple, a member of the Metropolitan Washington Council of Governments' anti-noise committee. "We wouldn't want to take a step back."

Last week D.C. Council member Betty Ann Kane, chairman of the COG panel, told the House subcommittee that any federal noise policy should be a minimum standard to which local authorities would have the option to add restrictions.

Airlines have stepped up calls for a federal noise policy in recent years, as airports throughout the country have implemented restrictions in response to increasing complaints from residents.

Because noise restrictions differ among airports, airlines must juggle their fleets to adhere to the noise limits, a practice industry officials say costs millions of dollars each year.

"It's like a crazy quilt," a spokesman for USAir said of the differing restrictions. "It affects everyone's costs, schedules and service."

Federal lawmakers have been reluctant to implement a federal noise policy because it could make the government legally liable for expenses involved in adhering to it. If, for instance, a local airport were to buy up residential land to comply with a federal noise policy, any homeowners forced out could seek damages from the U.S. government.

Airlines also support the plan in the Ford bill to end federal flight limits at National.

At National, which is limited to handling an average of 37 flights an hour, officials say any increase would force them to expand the airport's renovation program. They also say it could create chronic flight delays.