An evacuation slide is an inflatable slide used to evacuate an aircraft quickly. An escape slide is required on all commercial (passenger carrying) aircraft where the door sill height is such that, in the event of an evacuation, passengers would be unable to step down from the door uninjured (Federal Aviation Administration requires slides on all aircraft doors where the floor is 6 feet (1.8 m) or more above the ground).
Escape slides are packed and held within the door structure inside the slide bustle, a protruding part of the inside of an aircraft door that varies with aircraft size, door size and door location. In many modern planes, to reduce evacuation time, evacuation slides deploy automatically when a door is opened in an "armed" condition. Modern planes often indicate an armed condition with an indicator light.