The National Capital Planning Commission voted yesterday to soften its longstanding policy calling for closing National Airport to commercial airlines by 1995 as an unsafe, noisy airport too close to downtown Washington.

In adopting a new section of the comprehensive plan for federal facilities in the Washington region, the commission maintained its objections to the airport, but now called instead for "phasing out" National as a "major commercial airport" in the indefinite future.

The commission has been the only federal agency to favor major changes at National.

It now proposes that passenger volume be reduced to half the current levels by 1995--to 7 million to 8 million passengers a year. The city of Alexandria and the Coalition on Airport Problems, an umbrella group that favors less use of National and greater use of Dulles International Airport, support similar reductions.

"Of course we're disappointed" in the commission's change of policy, coalition secretary Sharon Donovan said, "but a 50 percent reduction in flights, to 7 million to 8 million at National, is what we're fighting for. We'd just like to see it before 1995."

Arlington County, the Metropolitan Washington Council of Governments and the federal Department of Transportation favor maintaining National as the major area airport with a limit of 14 million to 16 million passengers annually.

The planning commission voted for immediate studies on possible future uses of the airport site.

Among options to be studied are a limited federal airport for use of the president, Congress and foreign dignitaries, a general aviation airport for noncommercial flights, an office-industrial park with air service, an expansion of Crystal City and a major federal employment center, all with extensive park and recreation facilities on the site.

James Wilding, director of operations for both National and Dulles, said that the commission's action will have no effect on a $1.3 million study now under way on how to modernize National.

A separate safety study of National was begun last fall by the National Transportation Safety Board. National was included among a half-dozen airports in the safety study after Air Florida Flight 90 crashed at the 14th Street bridge, killing 78 persons in January 1982.