Anxious travelers across the U.S. felt a bit of relief Friday as airlines mostly stayed on schedule while still cutting more than 1,000 flights largely because of the government shutdown.

Plenty of nervousness remained, though, as more canceled flights are coming over the next week to comply with the Federal Aviation Administration’s order to reduce service at the nation’s busiest airports.

The order is in response to air traffic controllers — who haven’t been paid in nearly a month as the shutdown drags on — calling out of work in higher numbers as they deal with financial pressure.

While it’s left some passengers making backup plans and reserving rental cars, the flights canceled Friday represented just a small portion of overall flights nationwide.

Passengers still faced last-minute cancellations and long security lines at the 40 airports targeted by the slowdown, including major hubs in Atlanta, Dallas, Denver and Charlotte, N.C.

Airlines expect limited disruptions this weekend and stressed international flights are not expected to be affected.

If the shutdown persists much longer, and more controllers call out of work after they miss their second paycheck on Tuesday, the number of cancellations could jump from the initial 10% reduction of flights to 15% or 20%, Transportation Secretary Sean Duffy said on Fox News on Friday.

Not all the cancellations were due to the FAA order, and both United and American airlines said they were able to quickly rebook most travelers.

The airlines focused their cuts on smaller regional routes to airports where they have multiple flights a day, helping minimize the number of passengers impacted.

American, as an example, reported it was reducing flights from Dallas to Northwest Arkansas National Airport from 10 to eight per day.