supersonic.jpg A number of companies have announced efforts to bring back commercial supersonic transport. But, as this briefing outlines, the extraordinary negative environmental impact of these aircraft, especially the climate impact, is often overlooked. Such aircraft have very heavy fuel consumption demands and generate extreme non-CO2 effects, far exceeding those of sub-sonic aircraft. Policymakers should therefore be wary of facilitating the return of supersonic commercial flight, and devise measures to ensure that any potential reintroduction does not result in a net increase in civil aviation's climate impact compared to a 'no supersonic' scenario. This briefing outlines the extraordinary negative environmental impact of supersonic aircraft.