Air Force One is not a specific plane, but the official call sign for any United States Air Force aircraft carrying the president of the United States. In common usage, it refers to two specific Boeing 747-200B jumbo jets modified for presidential travel, designated VC-25A, with tail numbers 28000 and 29000. These planes have extensive security features and special accommodations for the president and staff, such as offices, kitchens, and conference rooms. These aircraft are based at Joint Base Andrews and have the capability for midair refueling, allowing for unlimited range. The VC-25A planes have been in service since 1991, and new Boeing 747 models meant to replace them have been scheduled for delivery since 2024.