Concourse B at Denver International Airport (DEN), one of United Airlines' main hubs, is where the airline primarily operates. There are many gates in Concourse B to handle United's wide range of flights United Airlines DEN Terminal both domestically and internationally. A number of passenger amenities are available at the airport, such as shops, restaurants, and United Club lounges for first-class passengers. Concourse B is conveniently accessible to passengers using the DEN subterranean rail system, which links all terminals and guarantees seamless airport transportation.