Officials at National Airport are nearing a decision on whether to test a controversial plan to divert low-flying jets from the Potomac River corridor and route them over residential areas that are now largely free of aircraft noise.

The so-called scatter plan, which proponents say would give deserved relief to communities along the Potomac and distribute noise more equitably across the area, would let pilots turn off the river soon after takeoff and pass over densely populated areas.

The plan, as currently worded, would permit jets to begin turning over Arlington just north of the Iwo Jima Memorial and over Northwest Washington near the Georgetown Reservoir. However, many of the planes would continue upstream before turning.

Planes taking off to the south could fly over Fairfax and Prince George's Counties and Alexandria once they reached the vicinity of the Woodrow Wilson Bridge, though many would continue south.

This would bring jets over communities across North Arlington and in Upper Northwest and Maryland, such as Spring Valley, Cleveland Park and Chevy Chase, and, to the south of the airport, over communities scattered along the Capitol Beltway corridor on both sides of the river.

The result, says James Wilding, director of National and Dulles International airports, will be "a lot of airplanes over a lot people who've never seen airplanes before."

Next month, the FAA plans to release an environmental study detailing how individual neighborhoods would be affected by the test. After public comment, the experiment might begin this fall and run 60 to 90 days, assuming a decision to proceed is made, according to Wilding. Implementing the scatter plan permanently would require further study and the approval of the Metropolitan Council of Governments.

Currently, about 260 passenger jets, plus some private executive jets, take off from National on a typical weekday. Most follow the river north to the Cabin John area or south to several miles beyond the Wilson Bridge, before banking and heading for their destinations.

Debated heatedly since the mid-1970s, the scatter proposal has pitted river corridor communities such as Palisades and Tantallon--where people have been angered for years by rattling crockery and interrupted patio conversations--against communities determined that their own skies will stay quiet.

"You have up to 300 overflights a day which are being imposed on one group of people," says Eric Bernthal, a Cabin John resident and president of the Coalition on Airport Problems (CAP), an umbrella organization of civic groups that pushed the scatter concept forward. The plan would give "as equitable a distribution of these flights as possible," he argues.

The scatter issue has caused the first serious rifts within CAP since it was formed in 1979 to coordinate the campaign for reduced traffic at National. Members from Arlington and Alexandria, backed by local government officials there, oppose the scatter plan, claiming it would unfairly shift the brunt of the noise to them and compromise safety.

"We already get it far worse than Cabin John or southern Prince George's," says Fred Wood, the Arlington County Civic Federation delegate to CAP. "The plane that bothers them bothers us a whole lot more" because it is lower and therefore noisier, he said.

Opponents of the scatter plan say the possibility of a plane hitting a TV tower or high building is less along the river corridor, and they argue that the water would be the best place to put down a crippled airplane.

Bernthal rejects the safety arguments, however, saying the river is too curvy to land on in many places and has many obstacles along its banks. Scattering the jets would foster safety, he maintains, by getting airplanes out of inhabited areas faster.

The Federal Aviation Administration has said that either way, acceptable standards of safety can be maintained.

The FAA, which owns and operates National, is devising the plan in response to a request from the Council of Governments, which in 1981 endorsed a test after rejecting the idea in earlier years. Preparations were put off after the air traffic controllers' strike in August 1981 and are now proceeding again.

Since shortly after jet service began at National in 1966, most planes have been kept over the river corridor, on the grounds the waters would absorb the worst of the noise and that the minimum number of homes would be affected. The traffic overhead has contributed to a scientifically measurable higher level of background noise in communities like Georgetown and Old Town Alexandria than in ones further from the airport.

The plan would reverse the old philosophy and assert instead that many people getting a little noise is fairer than a few getting a lot, proponents say. The departures would be fanned out, so that neighborhoods generally would not get more than several planes per hour overhead, they say.

The plan could not be totally equitable, however. The nearer a house is to the airport, the more common planes overhead would be. And much of the District would be shielded by the no-flight zone that takes in the Capitol and White House and Vice President's Mansion on Massachusetts Avenue. To avoid the mansion, planes flying upstream and wanting to turn east would have to continue farther upstream than those turning west into Virginia.

Arriving planes would not be affected by the plan. Nor would it alter noise reduction procedures by which pilots taking off are supposed to ease up on their throttles after reaching 1,500 feet.

Airlines have endorsed the plan because it would save fuel now burned on the current roundabout routes out of the metropolitan area. A spokesman for the Air Line Pilots Association said that pilots have no objection to it but will reserve judgment until operational details are available.

The plan has some strong opponents. Nine Arlington and Alexandria civic groups broke ranks with 36 other member organizations at the March meeting of the CAP and spoke against the plan, CAP president Berenthal said. The Arlington County Board and the Alexandria City Council have both issued resolutions against it.

The Fairfax County Federation of Citizen Associations, which claims 135 member organizations, and the Federation of Citizens Associations of D.C., which claims 23, both recently passed resolutions against the plan.

Opponents generally argue that planes belong with the river. Fewer people live there, they say, and most have come since 1966. "People who bought in there knew the planes were there," says William Crennan of the Fairfax County federation.

Some anti-National activists have suggested that, in the long run, a scatter plan could be a valuable organizing tool for them. Currently, only river corridor residents are concerned with the planes. But if the planes are spread around, the reasoning goes, that could stir up everyone and create new pressure for a related issue--sending flights to Dulles.