The Federal Aviation Administration ‘s unprecedented order to scale back flights nationwide because of the record-long government shutdown took effect Friday morning, with some passengers scrambling to figure out backup travel plans.

The 40 airports selected by the FAA span more than two dozen states and include hubs such as Atlanta, Dallas, Denver, Los Angeles and Charlotte, North Carolina, according to the order.

In some metropolitan areas, including New York, Houston, Chicago and Washington, multiple airports are being impacted, while the ripple effects could reach smaller airports as well.

Karen Soika from Greenwich, Connecticut, told her Uber driver she had to get to Newark Airport fast to catch her flight to Utah for a weekend trip. She had just learned it was rebooked for an hour earlier. But she later learned her plane was actually leaving from New York’s John F. Kennedy International Airport, instead, at least an hour away.

“I’m a surgeon, I’m used to chaos,” she said. She unsuccessfully tried to book a rental car.

“I’m going to U-Haul and I’m going to drive a truck cross country to get back to Utah,” said Soika, who’s advising on medical scenes there for a spinoff of the TV series “Yellowstone.”

Airlines scramble to adjust schedules

Airlines scrambled to adjust their schedules and began canceling flights Thursday in anticipation of the FAA’s official order, while travelers waited nervously to learn if their flights would take off as scheduled.

“We are operating today over 6,000 flights,” David Seymour, chief operating officer for American Airlines, told ABC’s “Good Morning America.” Now we’ve had to cancel as part of this directive 220 flights today and that will be the same number through the weekend, until we start ramping up. We have been working tirelessly throughout, around the clock, to ensure that we’re minimizing the disruption to our customers.”

Airlines directed passengers with plans into the weekend to check apps to learn their flight status.

Some passengers quickly searched for alternatives to flying. Hertz is reporting a sharp increase in one-way car rentals. One-way reservations have spiked more that 20% through the weekend, compared with the same period last year.

“We join the airlines in urging Congress to swiftly pass a clean continuing resolution and restore certainty for travelers,” wrote Hertz CEO Gil West. “Every day of delay creates unnecessary disruption.”

More than 815 flights have been called off nationwide, according to FlightAware. Delta Air Lines said it would scratch roughly 170 flights Friday, and American Airlines planned to cut 220 a day 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.”

FAA order comes as Trump administration pushes Democrats

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.