Like Stansted Airport, the American Air Museum at Duxford took ten years from design to completion, and in this case no environmental debates could be blamed for the delay. Perhaps because of its protracted development, this museum has not been fully credited with the critical role it played in Foster’s trajectory. The sweep of the light concrete shell, sophisticated and effortless like a glider in flight, is such an elegant and graceful geometrical gesture that it summarizes the spontaneous ease and clarity of the best Foster. Joining the cockpit simplicity of the Fal refuge with the elemental monumentality of the Sainsbury Centre, the shape of this celebration of aviation would reappear in countless other projects, from the stations of Bilbao and Canary Wharf to the project for the Sackler Gallery in Jerusalem or, indeed, the Crescent Wing of the Sainsbury. This extension, executed below ground and finished with a sloping curved skylight that opens to a lake and serves as a luminous plinth to the temple-like shell of the Sainsbury, is one of Foster’s most achieved and paradoxical projects: denying the extrusive technical logic of the container, which would demand a linear extension, the crescent closes an open building, enshrining it on a podium while exposing its productive fallacy...[+]