The term “jump seat” has several meanings, but most people use it specifically to refer to seats in aircraft which are designated for the use of cabin crew and certain guests of the airline. A jump seat may be located in the cockpit, or in the cabin of the aircraft, and as a general rule, paying passengers are not permitted to fly in jump seats. When cabin crew who are not on duty fly in a jump seat, this is known as jumpseating.
However, the origins of this term predate the invention of aircraft. “Jump seat” first appeared in the 1860s, to refer to a folding extra seat in carriages. When not in use, the jump seat could be neatly folded out of the way. Jump seats in carriages were often used by staff such as maids and chauffeurs, and they were sometimes located on the back of the carriage, or in a direction which would face away from the main occupants.
When the automobile was developed, many car manufacturers included jump seats in their designs, mimicking the features used in carriages. Such jump seats could provide extra seating for transporting a crowd, in exactly the same way that modern car jump seats are used today. As a general rule, you can find jump seats in vans and other large cars, and they are designed to fold into the floor so that they are out of the way when not needed. Many manufacturers tout their jump seats as a very useful design feature, allowing drivers to reconfigure the space in their cars as needed.
In aircraft, there are two types of jump seats. One type is found in the cockpit, typically against the back wall so that the person in it does not interfere with the operation of the plane. This jump seat is used for someone who is not involved in the operation of the plane, such as a visiting pilot, an airline official, or a government representative. Due to concerns about terrorism, access to the cockpit jump seat is tightly controlled.
Jump seats can also be found in the main cabin of many aircraft, for the use of flight crew. Flight crew sit in the seats for takeoff and landing, and then fold them back to keep emergency exits and aisles clear. By providing jump seats, airlines can ensure that they meet safety requirements for their cabin crew without using space which could be occupied by paying passengers.