United Airlines Holdings, Inc. is a holding company. The Company transports people and cargo throughout North America and to destinations in Asia, Europe, Africa, the Pacific, the Middle East and Latin America. The Company, through United Airlines, Inc., and its regional carriers, operates across six continents, with hubs at Chicago O'Hare International Airport (ORD), Denver International Airport (DEN), George Bush Intercontinental Airport (IAH), Los Angeles International Airport (LAX), Newark Liberty International Airport (EWR), San Francisco International Airport (SFO), Washington Dulles International Airport (IAD) and A.B. Won Pat International Airport (GUM). Its hub and spoke system allow it to transport passengers between a large number of destinations with frequent services. The Company has contractual relationships with various regional carriers to provide regional aircraft service branded as United Express. It provides freight and mail transportation services (Air Cargo).