A swing-wing is a type of pivoted wing planform that attempts to combine the advantages of a swept wing at high speeds, while avoiding its problems at lower speeds. The design is successful in this respect, but the added weight and complexity of the hinging systems is generally considered to be a greater cost than the advantages.
Swing-wing aircraft developed from earlier experimental aircraft that were built to study the effects of a swept wing. The first of these was the Messerschmitt P.1101 which allowed its sweep angle to be changed on the ground. A number of test flights were carried out at various angles to try to examine the tradeoffs. At the end of World War II the P.1101 was taken to the United States for futher study at Bell Aircraft, where further versions were built that could vary their angle in flight. One problem that was discovered while testing with this X-5 was that as the wing was pivotted rearward, the center of lift also moved to the rear, pushing the nose down. Some sort of system needs to be added to overcome this effect.
The swing-wing is only truly useful for those aircraft that fly at a wide range of speeds, and for this reason it has been used primarily in various military aircraft. The first production aircraft to use the system was the General Dynamics F-111, introduced in the late 1960s. This was followed by the F-14 Tomcat and MiG-23 in the 1970s.
A swing-wing was also used by Boeing's entry in the FAA's study for a supersonic transport, the 2707. However during the design stage it became clear that the mechanism was so large that it would leave almost no room in the cabin for seats. The design was later adbandoned in favor of a more "classic" delta wing.
With the introduction of relaxed stability flight control systems in the 1970s, the advantages of the swing-wing were reduced to some degree, and since that time no new swing-wing aircraft have been built.