The best inlet for pressure recovery at the inlet itself is one in the nose but that requires that the duct go around the cockpit and there are losses associated with a long duct. Simple side inlets increase the frontal area (drag) and ingest low energy boundary layer air that reduces pressure recovery. The NACA "flush" inlet was very clever in that the shape generates vortices that cause the boundary layer to spill out over the edge of the inlet. Nevertheless, as the F-93 proved, overall it was not as effective as an air intake for jet engines as a side inlet with boundary layer removal. It is, however, a go-to inlet for smaller volumes of air intake requirements and really looks racy. It was successful, or at least adequate to the task, on one airplane application, the air intake for the jet engine in the aft fuselage of the AJ Savage. One of its benefits in this instance was that it could easily be closed when the jet engine was not needed.