Airlines are canceling hundreds of flights to comply with the FAA's order. But there are still questions about the plan, which the agency says will keep the skies safe during the government shutdown.

The FAA’s phased mandate began Friday with a 4% reduction in operations and will increase to 6% by Tuesday, 8% by Thursday and 10% by Nov. 14. International flights are exempt, and airlines may choose which domestic flights to cancel to meet the targets.

Several airlines are offering the option to rebook or issue a refund for customers whose flights are impacted by the reductions.

The ongoing shutdown means that air traffic controllers at Denver International Airport have been working without pay, with many taking second jobs to try to make ends meet. Now, Colorado lawmakers are pushing for the Federal Aviation Administration to approve the airport's emergency waiver that would allow its air traffic controllers to be paid during the shutdown.

The government shutdown has triggered 1,000-plus flight delays as the FAA cuts capacity at 40 airports. Airlines are offering refunds and policy changes amid ongoing travel disruptions.

The Federal Aviation Administration has announced a 10% reduction in flight capacity across 40 major U.S. airports