"The skies shall be silent."

So read the sign on the door of Local 204 of the Professional Air Traffic Controllers Organization in Leesburg, where striking controllers milled about, waiting to resume their picketing for the afternoon shift at the Washington Air Route Traffic Control Center just outside town.

Spirits ran high among the strikers in Leesburg yesterday, both in the union hall and on the picket line. They were calmly defiant of President Reagan's threat to fire the strikers if they were not back on the job Wednesday morning.

Old-time union bravado and jaw-set confidence were the order of the day.

"Ronald yreagan will realize that we're not going to just stop and fold because he's trying to scare us," said local Vice President Jim J. Stakem. b"I wouldn't even consider going back to work under Mr. Reagan's threat. And I know quite a few controllers who are ready just to leave their profession because they can't stand the conditions."

About 150 controllers in Local 204, which lists more than 400 members in its bargaining unit, picketed the traffic control center from 5:30 to 8:30 in the morning.In the afternoon, the local went to the picket lines again, this time with about 80 controllers marching in front of the center beside Rt. 7.

As 10 state troopers and a dozen Loudoun County sheriff's deputies stood by with two police dogs, the picketers walked in an orderly circle. There were cries of "Scab!" when some controllers drove by the picket line to work the afternoon shift. Picketers snapped their pictures and recorded their names.

"We want to know who's for us and who's against us," said one controller who wore a Polish "Solidarity" button.

Union officials said that about half the normal afternoon shift reported for work, including 60 members of Local 204. For the day, they said, 150 controllers, or about 25 percent from the local, worked in spite of the strike. c

On the picket line, strikers said they were not surprised by the president's threat. Many added that although they did not believe Reagan would actually fire all the striking controllers, they were prepared for that.

"I think we're prepared for whatever sacrifice may come down the road," said Gregory M. Dubenitz of Midland, Va. "I've been living with the possibility of being fired for a year and a half because of the strike, but I think our ranks are secure."

"Anyway," said David G. Roseberry of Leesburg, "there's no way they can just take out all of us and just fire us. That's not a real viable threat, I don't think."

Roseberry, who broke off a family reunion on his vacation in Altoona, Pa., to make it to the picket lines for the afternoon shift, also questioned the wisdom of supervisors filling in for controllers.

"They don't know how to work the automated equipment," he said, adding that many of the controllers had not talked with airplane pilots in years.

When asked his view of the safety aspect, Roseberry replied: "Well, if there's no airplanes flying it's safe." CAPTION:

Picture; Jim J. Stakem, vice president of Local 204 of the Professional Air Traffic Controllers: "We're going to just stop and fold because he's [Reagan] trying to scare us." By James A. Parcell -- The Washington Post