Daily Digit is the story behind the numbers that make our world work. Today we’re looking at the world’s first hypersonic aircraft. The China Academy of Aerospace Dynamics says it has tested an aircraft with a top speed of 4,564 mph. That’s almost six times the speed of sound, and would make the Starry Sky-2 China’s first hypersonic aircraft. While the technology is still very much in the experimental stages, Boeing is planning a hypersonic future for passenger aircraft. Someday, flights from New York to London could take as little as two hours. Don’t miss your flight!