It's useful for reducing radar cross section. Moving control surfaces are a headache for RCS management. The F-22 uses "cat eye" slits between its control surfa

It's useful for reducing radar cross section. Moving control surfaces are a headache for RCS management. The F-22 uses "cat eye" slits between its control surfaces to minimize these radar blooms, but it'd better to do away with them altogether. It could also remove the need for those huge aerodynamic fairings on the CS actuators on jetliners, but then add some complexity and remove fuel volume in the wings.