Abstract: An improved boundary layer control system is particularly useful in applications where controlled air is to be injected into a boundary layer region adjacent to a surface of an aircraft wing. The controlled air is obtained from an air source having a temperature and a pressure which are substantially greater than ambient temperature and pressure, such as that obtained from a jet engine bleed air source. A number of manifolds are located in spanwise arrangement along the wing and serve to conduct the air from the source to a plurality of nozzle penums, each of which includes a plurality of spanwise-spaced apertures for injecting air into a portion of the boundary layer region. The manifolds are interconnected by compressible bellows and are mounted so that respective inboard ends are fixed and respective outboard ends are free to move longitudinally.