A gate, or gatehouse, is an area of an airport that provides a waiting area for passengers before boarding their flight. While the exact specifications vary from airport to airport and country to country, most gates consist of seating, a counter, an aircraft entry or exit doorway, and a jet bridge.
Domestic vs international
At most gates a single doorway opens to a jet bridge which leads to the aircraft door depending on aircraft model. If the gate is being used for departures,domestic arrivals or international arrivals coming from airports with pre clearance at that airport the door that goes to the waiting area will be opened and the hallways to customs will closed, preventing passengers from entering into the customs hall. For international arrivals that is coming from cities that does not have pre clearance, the door leading to the waiting area is closed and passengers are directed to a hallway where they can either go into the customs hall, if they end at that city, or clear customs and pre-board security, if they have a connecting flight.
Jet bridge vs airstair
Before the era of the jet bridge, or jetway, airline passengers embarked onto the aircraft from ground level via airstairs. If initially indoors, passengers would exit the waiting area through a door to the outside and then passengers would proceed to the airstairs leading to the aircraft door. This method is still used for boarding smaller planes or boarding at smaller airports.
- Freudenrich, Craig, Ph.D. "How Airports Work." HowStuffWorks. N.p., n.d. Web. 24 Nov. 2012. <http://science.howstuffworks.com/transport/flight/modern/airport3.htm>.