U.S. airline stocks, including Delta Air Lines, experienced a significant selloff following a warning from the U.S. Transportation Secretary about potential airspace closures. The threat stems from a prolonged government shutdown that has led to staffing shortages among air traffic controllers and airport security screeners. The Transportation Secretary stated that if the shutdown continues for another week, parts of the national airspace may need to be closed for safety reasons, which could lead to "mass chaos" with widespread flight delays and cancellations. This announcement has amplified concerns within the airline industry about operational stability and the financial impact of the ongoing political stalemate. In response to the secretary's comments, shares of major U.S. carriers, including Delta, United, American, and Southwest, fell between 3% and 5%. The industry is bracing for continued disruption as the shutdown persists, affecting millions of passengers and creating uncertainty for airline operations and revenue.