The YF-23 was designed to meet USAF requirements for survivability, supercruise, stealth, and ease of maintenance. Supercruise requirements called for prolonged supersonic flight without the use of afterburners. Northrop drew on its experience with the B-2 Spirit and F/A-18 Hornet to reduce the model's susceptibility to radar and infrared detection. The USAF initially required the aircraft to land and stop within , which meant the use of thrust reversers on their engines. In 1987, the USAF changed the runway length requirement to , so thrust reversers were no longer needed. This allowed the aircraft to have smaller engine nacelle housings. The nacelles were not downsized on the prototypes.