Investigators at the National Transportation Safety Board, concerned that a plane might hit a high-rise building in Rosslyn during a bad-weather approach to National Airport, want to remap the flight path to route planes farther from the buildings, according to aviation sources.

The proposals grew out of a board investigation of eyewitness reports that a Piedmont Airlines 737 jet passed unusually close to the USA Today building in Rosslyn during a cloudy approach on Dec. 28.

The incident, a year after an Air Florida 737 struck the 14th Street bridge, killing 78 people, fueled longstanding charges from civic groups that operating a busy airport close to downtown is inherently unsafe.

The Federal Aviation Administration, which owns and operates National, says the approach is safe and declined comment on the proposed change. "That approach has been in effect for years, and there hasn't been any trouble with it," said FAA spokesman Fred Farrar.

Drafted by safety board investigators, the proposals now are being reviewed by the board's five members. If approved by them, formal recommendations will be sent to the FAA, which is not required by law to implement them.

The Piedmont 737 was using a common bad-weather approach to National in which planes follow an electronic beam from the Cabin John Bridge area, descending to about 900 feet by the time they pass a point just upstream from Rosslyn.

The path takes them over the Potomac at Key Bridge, closer to the Rosslyn side than to Georgetown. Investigators are proposing shifting the beam to the northeast somewhat, so that planes would pass farther from the Rosslyn complex. It was not known how far the shift would go, or whether it would take planes over Georgetown.

Investigators also favor shifting the point at which pilots are required either to sight the ground during a bad-weather approach or circle and try again. That point is currently near Rosslyn.

In addition, investigators want the FAA to consider relocating National's main radar antennas, which lost track of the Piedmont plane briefly as it passed Rosslyn. Board investigators believe the antennas are poorly located, facing numerous obstructions from hills and buildings.

An FAA official familiar with National responded that the antennas are well located and track airplanes well, though he said the radar can lose sight of planes because of faulty transmitting equipment aboard the planes.

Farrar said the FAA is continuing to investigate the Piedmont incident.

Civic groups have argued for years that routing jets at low altitudes close to tall buildings posed a safety hazard. But they have generally favored sending airplanes to Dulles International Airport rather than changing the route into National.

Investigators' proposals constitute a "patchwork approach" to the problem, said Eric Bernthal, president of the Coalition on Airport Problems. If a plane is kept away from Rosslyn, "all you do is put it over the Watergate," he said.

The board's investigation was done as part of a larger inquiry into airport safety. It is looking at National and a dozen other U.S. airports in detail and will issue a report in late summer or early fall.