A penetrator is a long-range bomber aircraft designed to intrude and penetrate enemy defenses. The term is mostly applied to aircraft that fly at low altitude in order to avoid radar, a strategic counterpart to the shorter-ranged tactical interdictor designs like the TSR-2 and F-111. However, the term can be applied to any aircraft that is designed to survive over enemy airspace, and has also been used for the penetration fighter designs that were designed to escort the bombers.
The classic penetrator design is the Rockwell B-1 Lancer, where the term was first widely used.[a] The larger Tupolev Tu-160 is also a member of this class. Other aircraft, like the Boeing B-52 Stratofortress and some versions of the F-111 have also been adapted to this role. More modern designs, like the Northrop Grumman B-2 Spirit, can be technically classified as penetrators, but the term is not generally applied to these aircraft. However, the mission for the Next-Generation Bomber has been described as "penetrate and persist".