Within the terminal, passengers purchase tickets, transfer their luggage, and go through security. The buildings that provide access to the airplanes (via gates) are typically called concourses. However, the terms "terminal" and "concourse" are sometimes used interchangeably, depending on the configuration of the airport.
Smaller airports have one terminal while larger airports have several terminals and/or concourses. At small airports, the single terminal building typically serves all of the functions of a terminal and a concourse.
Some larger airports have one terminal that is connected to multiple concourses via walkways, sky-bridges, or underground tunnels (such as Denver International Airport, modeled after Atlanta's, the world's busiest). Some larger airports have more than one terminal, each with one or more concourses (such as New York's John F. Kennedy International Airport). Still other larger airports have multiple terminals each of which incorporate the functions of a concourse (such as Dallas/Fort Worth International Airport).
According to Frommers, most airport terminals are built in a plain style, with the 'concrete boxes of the 1960s and 1970s generally gave way to glass boxes in the 1990s and 2000s, with the best terminals making a vague stab at incorporating ideas of "light" and "air"'. However, some, such as Baghdad International Airport, are monumental in stature, while others are considered architectural masterpieces, such as Terminal 1 at Charles de Gaulle Airport near Paris or Terminal 5 at New York's JFK Airport. A few are designed to reflect the culture of a particular area, some examples being the terminal at Albuquerque International Sunport in New Mexico, which is designed in the Pueblo Revival style popularized by architect John Gaw Meem, as well as the terminal at Bahías de Huatulco International Airport in Huatulco, Oaxaca, Mexico, which features some palapas that are interconnected to form the airport terminal.
Due to the rapid rise in popularity of passenger flight, many early terminals were built in the 1930s–1940s and reflected the popular art deco style architecture of the time. One such surviving example from 1940 is the Houston Municipal Airport Terminal. Early airport terminals opened directly onto the tarmac: passengers would walk or take a bus to their aircraft. This design is still common among smaller airports, and even many larger airports have "bus gates" to accommodate aircraft beyond the main terminal.
A pier design uses a small, narrow building with aircraft parked on both sides. One end connects to a ticketing and baggage claim area. Piers offer high aircraft capacity and simplicity of design, but often result in a long distance from the check-in counter to the gate (up to half a mile in the cases of Kansai International Airport or Lisbon Portela Airport's Terminal 1). Most large international airports have piers, including Chicago's O'Hare International Airport, Larnaca International Airport, Frankfurt International Airport