Flight chaos grips US airports as some airlines advise booking 'backup ticket': See the list

Over 1,000 flights are now experiencing delays as flight cancellations grow during the government shutdown.

As of 10:45 a.m. ET on Thursday, 1,615 flights within, into or out of the U.S. had been delayed, while 49 had been canceled, according to FlightAware.com.

The Federal Aviation Administration (FAA) implemented a flight reduction plan limiting air travel capacity at 40 airports.

AMERICANS COULD FACE AIRPORT CHAOS IF DEMS DON'T END SHUTDOWN, TRUMP OFFICIAL WARNS

Transportation Secretary Sean Duffy told "Fox & Friends" on Thursday travelers might see additional delays.

"Now, does that mean there's going to be no delays? No … there's potentially still going to be delays if we have staffing triggers, and we don't have enough controllers in an aerospace where we did cut 10%, you might see additional delays," said Duffy.

Many airlines are updating customer policies and warning travelers of potential itinerary updates.

Here are a few worth noting. 

United Airlines CEO Scott Kirby updated employees in a press release about the impact of FAA reductions.

"United's long-haul international flying and our hub-to-hub flying will not be impacted," wrote Kirby.

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The Chicago-based airline is offering refunds to customers who do not want to fly during imposed restrictions on flights, "even if their flight isn't impacted."

Travelers will be notified if there are any changes to their flight through the United app, website and push notifications.

Southwest Airlines is evaluating how the flight restrictions will "affect our schedule and will communicate directly with customers as soon as possible," according to the company's website.

The Dallas-based airline is reminding travelers they must cancel their reservations at least 10 minutes prior to the scheduled departure time in accordance with airline policy.

American Airlines wrote in a press release that the company "expect[s] the vast majority of [its] customers' travel will be unaffected."

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However, American says it will reach out to customers as schedule changes are made.

The Fort Worth, Texas-based airline is placing pressure on Congress, emphasizing the strain on the aviation industry.

"We continue to urge leaders in Washington to reach an immediate resolution to end the shutdown," the release added.

Frontier Airlines will waive change or cancellation fees for flights between Nov. 6 to Nov. 12, and travelers will be refunded through travel credits for their itinerary, the company said. 

Frontier CEO Barry Biffle shared travel advice with followers on Instagram.

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"If you are flying Friday or in the next 10 days, and need to be there or don't want to be stranded, I highly recommend booking a backup ticket on another carrier," wrote Biffle.

Delta said it is also expecting to "operate the vast majority" of its flights as scheduled. 

The company said it is providing "additional flexibility" to customers with changes, cancellations or refund requests.

Duffy said Americans should still book holiday travel if they see deals they would like to grab, but also said it is "hard to predict" what may happen.

"As we come into Thanksgiving, if we're still in the shutdown posture, it's going to be rough out there. Really rough," said Duffy. "And we'll mitigate the safety side, but will you fly on time? Will your flight actually go? That is yet to be seen, but there'll be more disruption."

Speaking to Fox News Digital on Thursday morning, James Squires, director of the flight Desk at Travelmation Flights, said, "Given the possible reduction in scheduled flights, the airlines will try to rebook canceled flights to the next available flight. It is best for travelers to remain calm and to check with [their] airline's website or mobile app with their confirmation code to check on flight status."

He added, "If a traveler has flexibility and wants to make a voluntary change, the airline may offer them a chance to reschedule their flight to an earlier time or to reschedule their trip altogether. Some of the airlines are also offering clients the opportunity to cancel and still receive refunds on nonrefundable tickets. Travelers should confirm with the airline before canceling."

Rachel Wolf of Fox News Digital contributed reporting.