The Federal Aviation Administration (FAA) is set to implement an unprecedented order on Friday morning, reducing flights across the country due to the ongoing government shutdown, which has reached record lengths.

This directive from the FAA affects 40 airports across more than 24 states, including major hubs such as Atlanta, Dallas, Denver, Los Angeles, and Charlotte, North Carolina.

Several metropolitan areas, such as New York, Houston, Chicago, and Washington, will see multiple airports impacted by this order. The effects are also likely to be felt at smaller regional airports.

Airlines rushed to revise their flight schedules and began canceling flights on Thursday, preparing for the FAA’s official directive. Meanwhile, travelers with weekend and future plans are anxiously waiting to see if their flights will proceed as scheduled.

Across the nation, over 810 flights have already been canceled, according to data from FlightAware. Delta Air Lines announced it would cancel approximately 170 flights on Friday, and American Airlines plans to cut 220 flights daily through Monday.

The FAA said the reductions would start at 4% and ramp up to 10% by Nov. 14. They are to be in effect between 6 a.m. and 10 p.m. and impact all commercial airlines.

The agency said the cutbacks are necessary to relieve pressure on air traffic controllers who have been working without pay for more than a month. Many are pulling six-day work weeks with mandatory overtime, and increasing numbers of them have begun calling out as the financial strain and exhaustion mount.

“You can’t expect people to go in to work when they’re not getting a paycheck,” said Kelly Matthews of Flat Rock, Michigan, a frequent business traveler who has canceled most of her upcoming trips. “I mean it’s not a matter of them not wanting to do the job — but you can’t afford to pay for gas, your day care and everything else.”

The order comes as the Trump administration is ramping up pressure on Democrats in Congress to end the shutdown.

Airlines said they would try to minimize impact on customers. Some planned to focus on slashing routes to and from small and medium-size cities.

Carriers are required to refund customers whose flights are canceled but not to cover secondary costs such as food and hotel accommodations unless a delay or cancellation results from a contributing factor that is within the control of the airlines, according to the Department of Transportation.

Industry analyst Henry Harteveldt warned that the reductions will “have a noticeable impact across the U.S. air transportation system.”

The cuts could also slow package service as two airports on the list are major distribution centers for delivery companies: FedEx in Memphis, Tennessee, and UPS in Louisville, Kentucky, the site of this week’s deadly cargo plane crash.

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Associated Press journalists Hallie Golden in Seattle, Safiyah Riddle in Montgomery, Alabama, and Wyatte Grantham-Philips in New York contributed.