Abstract: Adaptive wing systems and aircraft. A variable-span wing for aircraft comprises a fixed-section (1) with skin (118) that forms a lift-generating wing surface, and further comprises a top and a bottom moveable section (2) that are vertically offset from one-another and which translate in substantially lateral directions into and out of the fixed-section (1) through fixed-section tip-openings (126). The moveable sections (2) overlap inside of the fixed-section (1) when fully retracted. The wing also comprises at least two tracks (310,316) and track-mating parts (320). The track-mating parts (320) are attached near the roots of the moveable sections (2) and translate along the tracks (310,316) to guide the moveable sections (2). A non-overlapped wing with motors (331) that translate with the moveable sections (2) and which have attached gear heads (332). A rack (341) is located within the fixed section (1). Rotation of the gear heads (332) against the rack (341) causes the moveable sections (2) to translate.