Headquartered in Chicago, United Airlines (UA) is world's largest airline when measured by the number of destinations served. The carrier, which was founded in 1926, flies to 375 destinations in 60 countries spanning North America, South America, Europe, Asia, Africa and Oceania. About one-third of its destinations are domestic. A founding member of the Star Alliance, United Airlines also has codeshare agreements with 12 other carriers. United operates nine hubs in the United States, Guam and Japan, including Houston's George Bush Intercontinental Airport (IAH) and O'Hare International Airport (ORD). Its fleet of 715 aircraft includes both Airbus and Boeing jets. Configurations vary depending on the type of plane and whether it's used for short-haul or long-haul routes, but may include First Class, Business Class, Economy Plus Class and Economy Class cabins.