Projects for both large-scale and business jet (see lower) passenger supersonic and hypersonic airliners (Aerion SBJ, HyperMach SonicStar, Next Generation Supersonic Transport, Tupolev Tu-444, Gulfstream X-54, LAPCAT, Reaction Engines A2, Zero Emission Hyper Sonic Transport, SpaceLiner, etc.) were proposed and now are under development.
In the 21st century some supersonic airliners and business jets (Aerion SBJ, HyperMach SonicStar, Next Generation Supersonic Transport, Tupolev Tu-444, Gulfstream X-54, LAPCAT, Reaction Engines A2, Zero Emission Hyper Sonic Transport) were under development.