Two passenger jets flew too close to each other near Charlottesville Monday night, the second such incident over Virginia in 10 days, the Federal Aviation Administration confirmed yesterday.

Members of the National Air Traffic Controllers Association, the controllers' union, said the incidents reflect low staffing levels at the FAA's Washington Air Route Traffic Control Center in Leesburg, which handles thousands of flights a day in the mid-Atlantic region.

"It is so unsafe," said Hugh McClure, vice president of the union local. "This is crazy."

FAA officials believe the staffing at Leesburg "is sufficient," said spokeswoman Jo Ann Sloane.

FAA investigators said they will visit the center today to determine the cause of Monday's incident, which occurred at 9:15 p.m. as Pan American World Airways Flight 505, a Boeing 727 carrying 132 people from New York City to Orlando, Fla., was flying above Gordonsville, Va., at an altitude of 28,000 feet.

United Airlines Flight 1015, a Boeing 737 with 41 aboard on the way from Dulles International Airport to Atlanta, was climbing from an altitude of 27,000 feet to 35,000 feet. Neither plane took evasive action, but given the speeds of jet aircraft in flight, the margin of error is very small.

At their closest, the aircraft were separated by 3.8 miles horizontally and 500 feet vertically, FAA records show. Federal rules prohibit commercial passenger jets from flying closer than 5 miles apart horizontally and 1,000 feet vertically.

Neither jet crew reported the incident, the airlines said, but the violation was automatically recorded as an "operational error" by the computers used by controllers to monitor and guide airplanes.

It was the second error in Leesburg-controlled airspace since June 30, Sloane said.

The controllers guide aircraft through the 118,000 square miles of airspace from New York to South Carolina and from the Atlantic Ocean to the Ohio River, including traffic to and from the busy airports of the New York, Philadelphia, Baltimore and Washington areas.

The Leesburg controllers' work is particularly tricky during the summer, when heavy traffic and thunderstorms disrupt flights up and down the East Coast. Union members said that Monday's incident occurred when storms had forced many planes out of standard flight paths.

Staffing levels at the FAA's 20 air route centers have been an issue since President Reagan fired 11,400 controllers for illegally striking in August 1981.

Before the strike, Leesburg's 342 fully qualified controllers and 85 trainees directed 1.6 million aircraft a year. Now the center handles more traffic with 252 fully trained controllers and 160 trainees.

Nine years later, the FAA says it is still rebuilding the controller force, and that overall staffing at Leesburg has grown in the last year to 481 positions as of June 30 -- including administration and support staff -- from 444 the year before.

"The staffing is safe," said center manager Joyce A. Sexton.

Controllers are making fewer errors because of newer, faster computers and the FAA's new methods of managing air traffic flows on a national rather than regional basis, officials said.

Leesburg controllers have made 26 errors so far this year, down from 34 during the same period of the year before, Sexton said. That is a 2 percent increase over the number they handled in the same period of the fiscal year before, Sloane said.END NOTES