Congress, the members of which are among National Airport's best customers, increased pressure on the Federal Aviation Administration yesterday to do nothing that would reduce the number of flights at the convenient airport.

While the House aviation subcommittee was hearing FAA officials yesterday explain proposals that would cut flights, 67 members of Congress introduced a nonbinding resolution against any such action.

And Rep. Glenn M. Anderson (D-Calif.), chairman of the subcommittee, said in an interview that the FAA should wait until his committee reports on the subject before adopting a final National Airport policy.

The FAA, as National Airport's owner and operator, technically has the authority to make its own regulations. In practical terms, however, Congress holds enough cards to strongly influence FAA decisions. At present, for example, Congress has before it in various stages three bills important to the FAA and could easily delay or amend them to prevent the FAA's boss, Transportation Secretary Neil Goldschmidt, from issuing his promised final policy on the airport in August.

The resolution was introduced by Rep. Marilyn Lloyd Bouquard (D-Tenn.) and signed by 66 other members of Congress. It said in part:

"It is the sense of the House of Representatives that neither the secretary of transportation nor the administrator of the Federal Aviation Administration shall promulgate any regulations or take any actions which would result in a reduction of public air service into Washington National Airport."

The resolution was referred to the aviation subcommittee.

The panel held its third day of hearings on the airport yesterday and heard representatives from cities and airlines fight to maintain or improve their position at the world's 16th busiest airport.

At issue is a proposed FAA policy that would:

Reduce commercial airline flights by about 20 percent daily.

Impose an absolute 10:30 p.m. to 7 a.m. ban on all but emergency flights.

Extend from 650 to 1,000 miles the distance that nonstop flights to and from National would be permitted.

Limit passengers at National to 18 million annually. National passed 15 million this year.

Airport directors from Louisville and Norfolk said that if the present 650 mile limit were extended and the number of flights reduced, they would lose nonstop flights to larger cities such as Birmingham or Kansas City.

Frank J. Ward, assistant director of the airport authority in Houston, said there should be no limit, since 1,000 miles just barely excludes his city. "We have the passengers," he said. ". . . We're not asking for increased slots (flights), we're asking for a competitive situation."

Thomas H. Davis, president of Piedmont Airlines, said in a statement that the proposed policy would result in reduced service by Piedmont to 21 of 25 cities it serves in six nearby states.

Benjamin G. Griggs Jr., vice president of Northwest Airlines, testified that Washington National "belongs to the people of the United States and to the extent that it can operationally handle a given number of aircraft those aircraft should be as large as possible."

Northwest, along with Eastern Airlines and some others, is particularly eager to win approval to use widebody airliners.

Marilyn Cable, one of six area residents who testified on behalf of various citizen groups, gave the most emotional speech of the day when she said they (jetliner) "noise interferes with the ability of people to perform normal functions of everyday life. Try to carry on a converstaion with a neighbor on the sidewalk. Try to listen to the news on TV or radio . . . Try to get your children to sleep with jets flying overhead every 45 seconds or so . . . A 30-mile stretch of the Potomac River has become a sewer of noise."

Robert Aaronson, associate FAA administrator, said the agency considers wide-body jet flights to National to be as safe as flights by other airplanes. w

However, he said, because of safety questions raised last week in these hearings by the Air Line Pilot Association, the question will be studied again before the final policy is released.

Eastern Airlines Capt. Thomas Bution, senior vice president for flight operations, said, "I can assure you that Eastern would not advocate the introduction of the (wide body) A300 unless we were absolutely convinced that it was operationally feasible. As a pilot, I would find any comprising of basic operational requirements unacceptable."

The crux of the problem was best explained yesterday in an exchange between Houston's Ward and Rep. Gene Snyder (R-Ky.), whose district includes the Cincinnati Airport -- a likely candidate to lose some service under the FAA proposal.

"I hope you understand our problem," Ward said.

"I understand your problem," Snyder said. "And I understand mine."