other flight crew or passengers on board. Gliders usually have no fuel or engines, although some variations such as motor gliders and rocket gliders have them for temporary or optional use. Pilots of manned fixed-wing aircraft usually control them from inside a cockpit, usually located at the front or top of the fuselage, equipped with controls and usually windows and instruments. Aircraft often have two or more pilots, with one in overall command (the "pilot") and one or more "co-pilots". On larger aircraft a navigator is typically also seated in the cockpit as well. Some military or specialized aircraft may have other flight crew members in the cockpit as well. In small aircraft, the passengers are typically seated behind the pilot(s) in the same cabin, although occasionally a passenger seat may be beside or even in front of the pilot. Larger passenger aircraft have a separate passenger cabin or occasionally cabins which are physically separated from the cockpit. Wings vs. bodies Flying wing A flying wing is a tailless aircraft which has no definite fuselage, with most of the crew, payload and equipment being housed inside the main wing structure. The flying wing configuration was studied extensively in the 1930s and 1940s, notably by Jack Northrop and Cheston L. Eshelman in the United States, and Alexander Lippisch and the Horten brothers in Germany. After the war, a number of experimental designs were based on the flying wing concept. Some general interest continued until the early 1950s, but designs did not necessarily offer a great advantage in range and presented a number of technical problems, leading to the adoption of "conventional" solutions like the Convair B-36 and the B-52 Stratofortress. Due to the practical need for a deep wing, the flying wing concept is most practical for designs in the slow-to-medium speed range, and there has been continual interest in using it as a tactical airlifter design. Interest in flying wings was renewed in the 1980s due to their potentially low radar reflection cross-sections. Stealth technology relies on shapes which only reflect radar waves in certain directions, thus making the aircraft hard to detect unless the radar receiver is at a specific position relative to the aircraft – a position that changes continuously as the aircraft moves. This approach eventually led to the Northrop B-2 Spirit stealth bomber. In this case the aerodynamic advantages of the flying wing are not the