Airport

An Airport is a facitilty for airplanes, jets, helicopters and other aircraft. There are several types of airports. A commercial airport is one served by commercial aircraft and airlines, as well as mail-carrier airlines. They can be international (one that has been approved by the government to fly internationally or has approved immigration), or regional (usually smaller commercial airports that are limited to flying just in that "Country" or "Region"). Commercial airports usually have a terminal building consisting of a check-in area, security checkpoints (TSA for the United States), and passenger gate areas. Once past security, some airports' terminals are divided into "wings" or "sections" (often called "Concourses"). Other airports, usually international ones, have separate terminals (each with their separate check-in areas, security checkpoints and gate areas). Heliports are another type of airport, many of which are located on news-station headquarters or on the literal roof of a hospital. Other airports, called "General Aviation" airports, do not have the required facilities for commercial air service, and have smaller runways that would not accommodate jets. All airports are given a "three-character code" or "IATA code" used by the FAA to differentiate airports. For example, London Heathrow Airport would be LHR and New York John F. Kennedy Airport would be JFK.

Airports were awesome before 9/11. Security lines were much shorter and quicker (Video Here of CVG airport, 2000), with profoundly less requirements than post-9/11 (e.g. you didn't have to remove your shoes). Most checkpoints were controlled by officers of the respeced city, but were replaced by the TSA. Many airports, much of which updated since 2001, used to have a "flight-observer deck", an area of the airport where passengers could easily watch planes take off. Many airplane passengers (especially kids) were sometimes invited to watch the pilots control an airplane during flight. However, barrier doors were added to prohibit third-party members from entering the cockpit.

World's Busiest Airports by Passenger, 2016
To be added very soon.