Abstract: A collapsible wheelchair conveniently switchable between deployed and stowage modes resists bending and torsional distortion. The wheelchair narrows for negotiating narrow airplane aisles, and it may be broken down or reassembled in the field without special tools. A rigid, generally cubicle, wheeled frame is foldable between deployed and retracted orientations. Drive wheels can be independently removed to narrow the wheelchair to clear restricted spaces. The frame supports a removable chair equipped with removable arm rests and an adjustable foot rest. The chair is mounted to a power pack centered between the opposite frame sides and mechanically interconnected by a pair of similar, spaced apart parallelogram linkages. The power pack comprises a pair of synchronized pneumatic cylinders coaxially disposed within separate tubular, extensible sleeves. Each parallelogram linkage comprises separate metallic links occupying a plane perpendicular to the frame sides for synchronizing side movement.