There's a reason the Boeing 2707 was cancelled, and that no new supersonic transport has flown after 1969; because we don't need them. A 747 going 85.5% the speed of sound over the atlantic ocean with 400 people on board isn't only more economical for the airline and the passenger, but the 747 can be used anywhere that a suitable airport exists! A Concorde, or any supersonic transport can't be flown coast to coast in the United States, the sonic boom cause great annoyances, and are loud even at 50-70,000ft. When the Concorde was delivered to the Museum of Flight in Seattle, they had to do a special trip over the Canadian wilderness, up towards the arctic circle, so they could say that Concorde's clast flight was supersonic