What You Need to Know: The SR-72, developed by Lockheed Martin’s Skunk Works, is a proposed hypersonic reconnaissance aircraft aimed to fill critical intelligence gaps in the U.S. Air Force.

A Chinese firm says it expects to fly a supersonic prototype in the second half of this year, with the goal of eventually flying a more advanced hypersonic commercial jet by 2030 at Mach 5 (3,836 ...