United Air Lines is a major American airline headquartered in Chicago, Illinois. It operates a vast network of domestic and international flights, serving millions of passengers each year. Founded in 1926, the airline has grown to become one of the largest in the world, offering a range of services including economy, business, and first-class travel. The airline is a member of the Star Alliance, a global airline alliance that enhances connectivity and travel options for passengers. United Air Lines is known for its extensive route network, modern fleet, and commitment to customer service, making it a popular choice for travelers.