Follow our coverage from Republic reporters of the effect of the federal government shutdown on air travel and Phoenix Sky Harbor flights.

A small percentage of domestic flights were canceled on Friday, but Transportation Secretary Sean Duffy said the reductions, which were already going to increase next week, could sharply rise by the holidays if the shutdown continued.

UPDATE: 3:40 p.m.: Austin-Bergstrom International Airport announced the FAA had lifted its ground delay as of 3:34 p.m. However, George Bush Intercontinental and Houston Hobby are both seeing ground delays of 46 minutes and 2 hours 46 minutes respectively, according to the FAA.

The FAA said it is reducing flights in Philly and other cities to alleviate pressure on air traffic controllers amid the government shutdown.

About 3 percent of Friday’s flights were canceled because of the government shutdown. The percentage could rise to 20 percent as the holidays approach.

Transportation Secretary Sean Duffy said Friday that flight reductions could go as high as 20 percent if the government shutdown drags on, as the Federal Aviation Administration (FAA) begins reducing flights by 10 percent due to air traffic controller staffing shortages.

Passengers on flights canceled due to the FAA order are entitled to a refund from the airline. While Knoxville's airport is not on the reduction list, travelers to and from 40 major hubs could be affected.

The FAA orders 10% flight reductions at 40 major U.S. airports starting Friday due to air traffic controller shortages during the government shutdown.