Airports in New York, Los Angeles and Chicago along with hubs across the U.S. are among the 40 that will see flights cut starting Friday due to the government shutdown, according to a list distributed to the airlines and obtained by The Associated Press.

The Federal Aviation Administration said Wednesday that it will reduce air traffic by 10% across 40 “high-volume” markets to maintain travel safety as air traffic controllers exhibit signs of strain during the ongoing government shutdown.

Airlines said they would try to minimize the impact on travelers. United Airlines said it would focus the cuts on smaller regional routes that use smaller planes like 737s.

Passengers should start to be notified about cancellations Thursday. The AAA recommended that travelers download their airline’s app and turn on notifications. United Airlines and Delta Air LInes both said they will offer refunds to passengers who opt not to fly -- even if they purchased tickets that aren’t normally refundable.