The Reagan administration's plan for National Airport may bar some of the noisiest jets, but it would allow increased numbers of airplanes to use National, especially at night, theWashington area's federal planning agency warned last week as it riticized and praised the new plan.

"We've been here before. Every time a new secretary (of transportation) comes in there's a new policy, which is roughly the same damn policy," said T. Eugene Smith, Virginia's member on the National Capital Planning Commission, at the commission meeting last week.

"This airport problem is one of the greatest messes we have in the nation's capital," added Smith, president of the National Bank of Fairfax, who was appointed to the commission last year by President Carter. The 1,000 planes a day that make National the world's sixth busiest airport also produce so much noise that "it means we can't use the Mall and the parks" around Washington, he said.

The federal planning agency voted unanimously to praise the new policy as "an important step" in planning for the future of National, but it also unanimously opposed several major features of the plan, including late-night flights and extension of the present 650-mile flight limit to 1,000 miles.

The commission also reaffirmed its previous positions that National should be closed by the year 2000, that the number of passengers using the airport should not be allowed to grow to 16 million, as recommended by the Reagan administration (about 14.5 million now use it annually) and that greater efforts should be made to make Dulles into the area's major airport, including extension of Metro or a light-rail train to Dulles.

The proposed plan will allow planes that meet certain noise standards, including quiet jets, to use National all night, ending the present 10 p.m. to 7 a.m. flight curfew.

The administration plan will go into effect in October unless blocked by Congress, which last year rejected the Carter administration plan for National.