United Continental Holdings (UAL) unites cities around the globe through its primary United Air Lines subsidiary. While United Air Lines is its main line, the company also has regional operations, which are operated under contract by United Express. Combined, the company handles an average of roughly 5,000 flights a day to more than 330 domestic and international destinations from hubs that include Chicago, Denver, Houston, Los Angeles, San Francisco, and Washington, DC. Like most airlines, the company sells the majority of its seat inventory through travel agencies and global distribution systems in addition to its main website.