Northern Virginia planners have rejected as out-of-date and inadequate new air traffic policies proposed for National and Dulles airports by the Federal Aviation Administration.

Citing a drastic drop in air traffic at Dulles this spring and summer, when the FAA study was being completed, the Northern Virginia Planning District Commission is urging the federal agency to reconsider the policy proposals announced in August.

Adoption of the policy -- delayed by Congress at least until next April -- would permit additional traffic at National, including use of larger planes and flights to farther destinations but, for the first time, would place restrictions on the airport's flight patterns and growth.

The Northern Virginia commission noted that National and the recently improved Baltimore-Washington International Airport have been luring air travelers away from Dulles. The commission pointed out that outbound Dulles flights have been carrying an average of 20 percent fewer passengers than in the early part of 1979. The new FAA policy could further accelerate the diversion of flights from Dulles, which was designed to be Washington's major airport.

The 11-year-old regional Northern Virginia planning agency, which had not taken a position on the federal policy, also objected to the FAA's proposed 17 million passenger limit for National. (Last year 15 million passengers used it.) In addition, the planning commission objected to proposals to increase the number of long-distance flights allowed from National, and to allow the use of wide-bodied jets at the airport.

Under federal regulations, the commission is required to comment on the policy as part of a court-ordered environmental review of the impact the changes would have on the areas surrounding National and Dulles.

In other business at its meeting last Thursday, the planning commission endorsed a proposal to include land-use planning in a long-range air pollution study to be conducted by the Metropolitan Washington Council of Governments.

Current air quality planning for the Washington area has relied primarily on short-term antipollution measures, most of which involve transportation. (Motor vehicles are the major cause of city air pollution, according to past reports). Land-use planning would include consideration of the impact of urban sprawl and zoning on air quality.

The commission also expressed concern over what it called an inadequate environmental review of Wayside Village, a housing development propsed in Prince William County.