An undated computer-generated handout image from the European defense group EADS shows the so-called "Zero Emission Hypersonic Transportation" (Zehst), an EADS project of a hypersonic commercial aircraft able to transport 50 to 100 people between Paris and Tokyo in 2.5 hours. The plane is not expected to be operational until around 2040, according to EADS officials, who unveiled the project at the Paris Le Bourget air show on June 18, 2011. AFP PHOTO/EADS

The model of a future commercial high speed transport system called ZEHST (Zero Emission High Speed Transport), a hypersonic aircraft using rockets and turbojet engines to take corporate customers from Paris to Tokyo in less than three hours, is prepared on the EADS stand at Le Bourget airport near Paris on June 19, 2011 a day ahead of the opening of the Paris International Air Show. This project is an EADS Innovation Works and Astrium project in partnership with the French ONERA national aerospace research laboratory. AFP PHOTO / ERIC PIERMONT