Whether the nation's air traffic control system can safely recover from the firing of 11,400 striking controllers comes sharply into focus 40 miles west of the Loop, in an enormous darkened room that is the heart of the Federal Aviation Administration's Chicago Air Route Traffic Control Center.

One seasoned controller who stayed after the strike by the Professional Air Traffic Controllers Organization (PATCO) was worried sick, he said, when he read recently that FAA Administrator J. Lynn Helms had told Congress the air traffic control system "is now capable of handling 100 percent" of the number of flights it handled before the strike.

At the Chicago center, the veteran controller said, "The experience level is as low as I've seen it in 25 years . . . . We've got controllers who have never held traffic in a thunderstorm before. We have a lot of cases where people's self-confidence exceeds their ability. They haven't been through enough yet."

The FAA, he said, "is flushing through mediocre controllers, and morale problems here are close to what they were before the strike."

The controller is tired, and spends at least half of his working hours training new controllers, a task far more taxing than pushing airplanes. The old pro sees John Bacon, new chief of the Chicago center, as just another old-line, hard-nosed, inflexible FAA bureaucrat, the type that is supposed to be disappearing because of the agency's new emphasis on "human relations."

Bacon has heard the complaint. It has to do, he said, with his insistence on continuous supervision in the radar room, not just at the radar screen. Quite apart from how well Bacon and his controllers get along is the fact that they agree the Chicago center is far from perfect.

"One of the things that concerns me," Bacon said, "is the inexperience level. We talk to O'Hare airport once in a while, and they tell us we gave them a plane too high or too fast. We've really got to keep our eye on the experience level.

"A controller doesn't really learn to control airplanes until he's on his own. We'd like the luxury of having more seasoning time."

The Chicago center was the place where controllers discovered whether they had the "right stuff." It was a tremendous ego trip: if it became very busy, a controller could be handling as many as 24 airplanes simultaneously, directing them into holding patterns or routing them around thunderstorms on their way to one of three active runways at O'Hare, the world's busiest airport, or 44 other airports in Indiana, Illinois and Wisconsin.

As many as 44 radar screens would be operating at once. Now they make do with 29. Three big sectors of responsibility have been transferred to the Cleveland center because Chicago could not handle them. More airspace is being transferred from the center to the radar room at the O'Hare tower, because O'Hare is in better shape.

The Chicago center was among the hardest hit by the PATCO strike. On the day of the strike, only 17 of 160 scheduled controllers showed up for the morning shift. The Chicago center will probably be the last of the 20 FAA centers to recover fully. No one, either in Chicago or in FAA headquarters, is predicting when that will be.