The US government shutdown is causing a 10% reduction in air travel capacity at 40 major airports, warns Transportation Secretary Sean Duffy. This decision comes as a result of air traffic controllers working without pay, leading to fatigue issues. The shutdown, now the longest in US history, has forced controllers to keep working without compensation, with some even taking on side jobs or calling in sick. The flight reductions will be gradual, starting at 4% of domestic flights on Friday, increasing to 5% on Saturday, 6% on Sunday, and reaching the full 10% next week. The affected airports, all high-traffic locations, will be announced on Thursday. This could impact between 3,500 and 4,000 flights per day. The FAA's Bryan Bedford emphasizes the need to maintain safety and efficiency, warning that further restrictions may be necessary if the shutdown continues. Southwest Airlines is assessing the impact on its services, urging Congress to resolve the impasse. Delta Airlines and other major US airlines have been contacted for comment. The situation highlights the challenges faced by aviation workers, with controllers struggling to make ends meet and a lack of predictability in their work.