“Is it safe? Yes, it’s safe. Can we survive this for long? That’s a question I don’t want to answer. I hope we can,” said Andrew ­LeBovidge, southwest regional vice president for the controllers union, who added that the shutdown is forcing colleagues to face questions they — and the nation — should not have to confront.

“Do you want a surgeon to be distracted by his financial problems when he’s operating on a cardiac patient — and for how long? The first patient? The second patient? The third patient?” LeBovidge asked. “Right now, the layers of the system remain intact because the controllers are diligently doing their work. But the distractions that are continuing to mount on their psyches are reaching levels they can’t endure for a long time.”

FAA documents released Tuesday show the agency is recalling more than 3,400 workers who had been furloughed but are now acknowledged to be vital for protecting “life and safety.”