United Airlines, founded in 1926 and headquartered in Chicago, serves over 300 destinations across more than 60 countries with a fleet of over 700 aircraft. As a founding member of the Star Alliance, United offers a variety of classes including Global First, Business First, and Economy, each with distinct amenities and baggage policies. The airline allows for the transportation of pets under specific regulations and provides several options for flight check-in and baggage management.