Just recently in Orlando, Florida, Boeing finally revealed the successor to the legendary Blackbird SR-71 spy plane. The caveat, this new model can fly at Mach 5. Yeah, 5 times the speed of sound.
Apparently these new models would be called "hypersonic" aircraft, and they would be mostly used for mostly military operations like covert reconnaissance and airborne assault. Apparently, Boeing is motivated because fierce rival, Lockheed Martin is releasing a similarly capable aircraft called the SR-72.
Boeing's hypersonics chief in a recent interview to Aviation Week Aerospace Daily gave details on the two-step development process for the new war plane. The first stage would consists of flight tests of an "F16-sized, single-engine" initial vehicle that acts as a "proof of concept". Then the second stage is the development of a "twin-engine, full-scale operational vehicle" that has roughly similar dimensions to the 107-foot-long SR-71.
Wow, this is all pretty cool stuff, but let me throw in some numbers. Mach 1, or the speed of sound is around 1235km/h. Thus, Mach 5 would be a stupendous 6,174km/h. 6,147km/h. That is the speed which the "son of blackbird is to travel at.
However, this is still at conceptual stage, though some actual work has been done.