AIRPASS was a British airborne interception radar and fire-control radar system developed by Ferranti. It was the world's first airborne monopulse radar system and fed data to the world's first head-up display. The name is an acronym for "Airborne Interception Radar and Pilot's Attack Sight System". In the Royal Air Force (RAF) it was given the official name Radar, Airborne Interception, Mark 23, normally shortened to AI.23. AIRPASS was used on the English Electric Lightning throughout its lifetime.