US airlines are quantifying the financial damage from the 43-day federal shutdown, with major carriers slashing Q4 earnings forecasts due to flight disruptions and booking declines. Southwest cut guidance to $500 million from $600-800 million, while Delta reported a $200 million hit driven by refunds and reduced bookings. The shutdown triggered FAA emergency orders requiring up to 10% flight cancellations at major hubs, affecting 5.2 million passengers. Industry analysts warn impacts will vary, with East Coast and Midwest-dependent carriers facing the steepest pressure as demand slowly recovers.