Although some flights leave from Terminal 2, United Airlines flies out of Terminal 1 at Chicago O'Hare International Airport (ORD) most of the time. Concourses B and C make up Terminal 1, sometimes United Airlines ORD Terminal referred to as the United Terminal, and are joined by an underground pedestrian tunnel. Numerous facilities are available at the terminal, such as United Club lounges, restaurants, retail stores, and services like ticketing and baggage claim. The O'Hare Airport Transit System (ATS) makes it simple for passengers to move between terminals, which facilitates more convenient connections.