New York City's three major airports -- JFK, LaGuardia and Newark -- are all among the 40 travel hubs around the country told to brace for delays and cancellations as the Federal Aviation Administration reduces air traffic. 

Hundreds of flight delays are being reported Saturday at the city's airports. Travelers nationwide are facing a slowdown with fewer planes taking off, causing plenty of uncertainty going forward. 

"We are in an unprecedented situation with the shutdown"

The FAA on Friday began its buildup to a 10% reduction in flights at 40 major airports, which sources say also includes Teterboro in Bergen County, New Jersey. The agency directed airlines to slash about 4% of flights nationwide Friday, but that number is expected to grow next week to up to 6% by Tuesday and 10% by Friday.

The agency says the cuts are necessary because air traffic controller staffing levels have become unsafe amid the government shutdown. 

"Number one, loss of separation in the airspace. So that's the minimum distance we keep between aircraft to keep them safe. We've seen breaches, more breaches, in regard to that loss of separation. We've seen more incursions on tarmacs throughout the country. And we have more complaints from pilots about stress from air traffic controllers and more complaints about the lack of responsiveness from controllers," Transportation Secretary Sean Duffy said Friday morning. 

The federal Department of Transportation says more air traffic controllers are calling out sick, further straining those on the clock who are working without pay. 

"If I have people who want to second guess what we're doing, why we're doing it -- I've done all I can to minimize disruption in the air space. I'm trying to get people where they want to go and get them there safely," Duffy said. "If people want to question us, I would throw it back at them, open up the government. If we have to take unprecedented action, it's because we are in an unprecedented situation with the shutdown."

Duffy warned the government could force airlines to cut up to 20% of flights if the shutdown did not end.

Peter Greenberg, travel editor for CBS News, says that things are going to get worse, and that it's not just our flights that are impacted, but the economy as well.

"Air is so intertwined with our economy that the economic impact here will be severe and exponentially bad if this continues beyond Tuesday," he said.

Airlines cutting hundreds of flights heading into weekend

Airlines are now scrambling to soften the blow for millions of travelers. For some perspective, American Airlines says it expects to cancel about 220 flights this weekend. United says it's canceling nearly 200 flights, and Delta says it's canceling about 170.

Travelers were beginning to grow weary Friday at Newark, with many stuck in terminals facing missed connections and long waits. Judy Helmhollz said her vacation to Johannesburg, South Africa, was sent into limbo. 

"Unfortunately, we had a full plane, lots of people stranded and a late night," she said. "The airport hotels are full, so I had to go to one that was 45 minutes away."

Another passenger said she had been stuck there since Thursday afternoon. 

"It was canceled without any notice," she said. "The flight for Friday has fully been booked, so we can only go for Saturday."

"I think the screws will be turned on the politicians in Washington, and they're going to take care of it before Thanksgiving. Trump doesn't want to cancel Thanksgiving," traveler Greg Joslyn said. 

"It's political gamesmanship. Eventually someone will cave. The question is how many people will be hurt before that happens," traveler Daniel Tynan said.

Depending on how long the government remains shut down, this could be the start of a much longer slowdown in the skies. 

Experts recommend travelers utilize websites like FlightAware, Flightradar24 and Flighty to track flights.

Airlines are looking to cancel in ways that will inconvenience the fewest people, like smaller flights on regional jets that carry up to 75 passengers. Some airlines are offering full refunds if customers decide they don't want to risk traveling during the shutdown.   

In the meantime, AAA advises anyone with an upcoming flight to familiarize themselves with their airlines' cancellation policies. The car rental company Hertz says it has seen a 20% increase in reservations for one-way bookings through the weekend, and the parent company for Greyhound buses says it is preparing to add capacity to its fleet.