SupersonicRichard Branson’s Virgin empire is now involved with a Silicon Valley-backed startup that wants to develop a small supersonic airliner. Branson, who once offered to buy British Airways’ fleet of Concordes before they were retired, is working with Boom Technology on plans for a 40-seat aircraft that could cruise at Mach 2.2 for the same ticket price as subsonic business class. Virgin Galactic has taken options for the first 10 aircraft and confirms its subsidiary, The Spaceship …