The union that represents air traffic controllers is raising concerns about furloughs of support staff.
The nation's 12,400 air traffic controllers are still working, but union leaders say 3,000 aviation safety professionals who support them are not.
A news release from the National Air Traffic Controllers Association calls it "akin to surgeons going into operating rooms alone."
At Sea-Tac Airport, controller Samantha Navarro says a stressful job is now more stressful.
"We have equipment that may or may not be working because there's nobody there," Navarro said.
Navarro pointed to the ground radar on top of the Sea-Tac tower, which helps controllers see planes in fog.
For the last couple weeks, it hasn't been working right.
"We've had it on, then it goes out again, then it's on and it goes out again," Navarro said.
Navarro says losing the radar is not an immediate safety hazard -- there's a work-around by asking pilots to radio in their positions
She says there are some maintenance people still on the job, but they appear to be working fewer hours and projects like fixing the radar are taking longer.
If the radar isn't working consistently when foggy weather arrives, Navarro says flights could be delayed.
Both Navarro and her husband are air traffic controllers and won't be paid until after the government shutdown ends.
"I'm quite stressed at home, but when I go through this gate, I have to put it all away and do my job," Navarro said.