SkyWest Airlines is an American regional airline headquartered in St. George, Utah, United States. SkyWest is paid to staff, operate and maintain aircraft used on flights that are scheduled, marketed and sold by a partner mainline airline. The company is contracted by Alaska Airlines, American Airlines, Delta Air Lines, and United Airlines. In all, it is the largest regional airline in North America when measured by fleet size, number of passengers carried, and number of destinations served.