Senate negotiators reviewing a far-reaching aviation bill have forged a compromise that would allow National Airport to maintain its nighttime noise restrictions.

The agreement, which would remove National from any less restrictive federal noise policy, came after Sen. Charles S. Robb (D-Va.) objected to any plan that would undermine current policies at National that prevent older, noisier planes from using the airport at night. It is the latest compromise on a proposal by Sen. Wendell H. Ford (D-Ky.) that could reshape noise policies and flight operations at some of the nation's busiest airports.

Airlines, frustrated by having to juggle their fleets to comply with noise limits that differ from airport to airport, have long sought a uniform federal policy, which they say would save them millions of dollars each year.

Ford's bill, which goes before a Senate budget committee this week, calls for a federal noise policy and outlines a slower phaseout of older, noisier aircraft than that planned at National and several other busy airports.

The compromise, under which National's existing noise policies would be retained even if a more lenient federal policy were approved, was seen as a positive sign by airport officials and anti-noise activists.

"We've said all along that we want to preserve what we have done as far as noise goes," said Hugh Riddle Jr., deputy general manager of the Metropolitan Washington Airports Authority.

Although many on Capitol Hill view passage of a federal noise policy this year as unlikely and no such measures have been proposed in the House, the issue has been prominent in the past two weeks.

In addition to the Senate measure, the House subcommittee on aviation recently conducted a series of hearings on a federal noise policy. Several airport operators urged the panel not to support legislation that would remove local control from noise policies.

Robb, like Ford a member of the Senate Committee on Commerce, Science and Transportation, also has engineered a compromise that would preserve daytime flight restrictions at National, currently limited to an average of 37 flights per hour.

Ford's bill initially proposed to end daytime flight limits at National, O'Hare International Airport in Chicago and LaGuardia and John F. Kennedy International airports in New York. Ending the limits would be a boon to airlines, especially carriers that have had difficulty breaking into the market at National because of the limited allocation of landing and takeoff rights.

Robb aides say the compromise would end the flight limits at the other three airports, and would open National to more carriers without adding more flights there. They said the plan calls for the FAA to create 30 "slots," or landing and takeoff times, that are not being used by carriers at National and redistribute them to carriers with fewer or no flights at the airport.

But airline officials interviewed yesterday were skeptical of the plan, and said they do not see how it could be implemented without taking flights away from major carriers at National.

"We use all the slots we have," said Jim Dare, vice president of schedules at American Airlines. "It would look like to me that they'd have to" take flights from larger carriers.