Hundreds of flights at the busiest airports in the U.S. are being scratched this weekend. Airlines are moving forward with reducing air service due to the lingering government shutdown.

Flight cancellations have started at Florida airports Friday, Nov. 7, and will gradually increase over the next week.

After the Federal Aviation Administration (FAA) ordered airlines to reduce traffic in 40 airports, many flights have already been cancelled.

More than 1,000 flights have been canceled and at least 5,000 delayed today, mostly due to a combination of air traffic controller staffing issues and an FAA-mandated 4% cut to flights because of the government shutdown.

Airports cutting flights include Atlanta, Charlotte, Boston, Seattle, and Philadelphia. See the list of airports most likely affected.

Flight cancellations across the U.S. could rise to 15%—or even 20%—if the government shutdown continues, Transportation Secretary Sean Duffy said.“If this shutdown doesn’t end relatively soon, the consequence is that more controllers don’t come to work,

The government shutdown entered its 38th day Friday, grounding nearly 1,000 flights and delaying about 3,000 more across the United States, according to federal aviation officials.

He also said that even if the government shutdown ends, flights won't return to normal instantly, as it will take time to restore staffing levels and schedules. Load any apps related to your airline or airport onto your phone -- they can send you information about delays and cancellations.

The bipartisan group of rank-and-file senators who have been negotiating a way out of the shutdown are mulling over a number of modifications to the bill. Lawmakers are expected to attempt to change the date that the short-term extension of government funding expires to a yet-to-be-determined later day.