These are the airlines most affected by the FAA’s order to cancel hundreds of flights during the government shutdown

• The FAA has ordered airlines to cut 10% of flights at 40 major airports.
• American Airlines canceled the most, over 200, as of Friday morning.
• There were four times as many cancellations compared to Thursday.

Hundreds of flights have been canceled on Friday since the Federal Aviation Administration ordered airlines to reduce traffic amid the government shutdown.

According to data from FlightAware, 818 flights within, into, or out of the US were canceled as of 7 a.m. ET.

That’s more than four times as many as Thursday’s 201. The preceding two days each had fewer than 200 such cancellations.

The aviation analytics firm Cirium recorded 748 cancellations on Friday, or 3% of all those scheduled to depart from the US, as of 6 a.m. ET.

It found American Airlines was the most affected, with 221 cancellations.

United Airlines canceled 184 flights, equal to 4%, followed by Delta Air Lines’ 173.

Southwest Airlines canceled 73, or just under 2% of its scheduled flights, per Cirium.

That was followed by Alaska Airlines’ 28 cancellations, Frontier Airlines’ 25, and JetBlue’s 24.

The FAA implemented an emergency order on Thursday to reduce traffic at 40 of the country’s busiest airports.

That will start at 4% of flights on Friday, before ramping up to 10% by November 14.

The government shutdown means air traffic controllers are working without pay. But now, on its 38th day, more of them are calling off sick, leading to understaffing and flight delays. The FAA said it needs to cut flight capacity to ensure it maintains the highest levels of safety.

United Airlines has so far provided the greatest detail on its mandated cuts. It said long-haul international flights and those between its hubs will be unaffected — while other domestic and regional flights will likely be impacted.

Data from FlightAware shows SkyWest Airlines has canceled the most flights, numbering 172, or 6% of those scheduled.

North America’s largest regional airline, SkyWest, operates flights on behalf of four mainline carriers. Such planes are branded as Alaska SkyWest, American Eagle, Delta Connection, and United Express.

The FAA said that airlines are required to give customers full refunds for cancellations.

Airlines may also try to rebook passengers on alternative flights. If you’re booked to fly over the coming weeks, they should directly inform you of any changes.