How Close Are We to Hypersonic Travel?

Imagine traveling from New York to London in just a couple of hours. Or waking up in California and flying to China in time for lunch. Hypersonic flight could advance travel in ways we haven’t seen since, well, the invention of flight itself. But flying at hypersonic speed isn’t easy. It presents incredible engineering and logistical challenges. So, how close are we to hypersonic travel?