U.S. airports in more than two dozen states are among those facing 10% reductions in air traffic Friday due to the government shutdown.

The Federal Aviation Administration is imposing the reductions to take pressure off air traffic controllers, who are federal employees and have gone without pay during the shutdown.

In addition to reduced flight traffic, the shutdown has led to more flight delays, with experts advising travelers to check flight statuses before heading to the airport, among other tips.

Here`s a closer look at what to know about the reductions.

The list includes 40 airports with Atlanta, Denver, Dallas, Miami, Newark and San Francisco among them. A full list of airports facing reductions is here.

Air traffic controllers have gone without paychecks during the shutdown of the federal government. That`s led to controllers calling in sick and contributed to staffing shortages that have been affecting air travel for weeks.

Most controllers work mandatory overtime six days a week during the shutdown without pay, the National Air Traffic Controllers Association has said.

That leaves little time for a side job unless controllers call in sick to the FAA.

They`re set to start Friday, with passengers expected to be notified on Thursday. Airlines have said people could see weekend travel plans disrupted with little notice.

It`s unclear when the reduced flights could end. Airlines, s and the travel industry have urged Congress to end the shutdown, which on Wednesday became the longest on record.

The cuts could include up to 1,800 flights and about 268,000 seats combined, according to one estimate.

United Airlines and Delta Air Lines both said they would offer refunds to travelers who opt not to fly, even if they have tickets that aren`t normally refundable.

The cuts also could disrupt package deliveries because two airports with major distribution centers are on the list. FedEx operates at the Memphis, Tennessee, aiport and UPS in Louisville, Kentucky, where there was a deadly cargo plane crash this week.

Transportation Secretary Sean Duffy warned this week there could be chaos in the skies if the shutdown drags on long enough for controllers to miss their second full paycheck next week.

FAA Administrator Bryan Bedford said this week that he`s never seen these kinds of measures taken before in his nearly four-decade experience in the aviation field.

"We`re in new territory in terms of government shutdowns," he said.

Staffing problems led to delays throughout October, but they were mostly isolated and temporary. Last weekend, though, saw a change.

From Friday to Sunday evening, at least 39 air traffic control facilities reported potential staffing limits, according to an Associated Press analysis of operations plans shared through the Air Traffic Control System Command Center system. The figure, which is likely an undercount, is well above the average for weekends before the shutdown.