When is a Gulfstream II or III not a Stage 2 aircraft? When it gets a Stage 3 hush kit. Last month, Miami-based Quiet Technology Aerospace delivered its 11th converted Gulfstream since its Stage 3 hush kit received certification a year ago this month. The latest two airplanes were GIIIs owned by charter operator C&S Aviation of Dallas. Quiet Technology said the conversion enables the aircraft to serve European and Pacific destinations without noise-related restrictions. To date, Quiet Technology has converted two GIIs, two GIIBs and seven GIIIs.