> At a speed of Mach 1.7, journeys times are supposed to be cut in half, with a flight form London to New York lasting 3:30 Hours (instead of 6:30)!<p>Add the time at the departure airport, 3 hours for international travel, and the time at the arrival airport for customs and collecting luggage, lets say another 2 hours, the difference in total journey time is 8:30 versus 11:30. This is definitely not a 50% reduction.<p>The fastest way of course is to use a private jet.