While Russia has deployed a number of Mach 2 bombers — like the Tu-22 Blinder and Tu-22M Backfire — these were not the fastest bombers that ever flew.
That title goes to the the North American XB-70 Valkyrie.
You haven't heard much about the Valkyrie – and part of that is because it never got past the prototype stage. According to various fact sheets from the National Museum of the Air Force, the plane was to be able to cruise at Mach 3, have a top speed of Mach 3.1, and it had a range of 4,288 miles. All that despite being almost 200 feet long with a wingspan of 105 feet, and having a maximum takeoff weight of over 534,000 pounds.
That performance was gained by six J93 engines from General Electric, providing 180,000 pounds of thrust.
The XB-70s had no provision for armament, but the production version of this bomber was slated to be able to haul 50,000 pounds of bombs – either conventional or nuclear. Imagine that plane being around today, delivering JDAMs or other smart weapons.
With the performance and a weapons load like that, buying this plane to supplement the B-52 should have been a no-brainer, right? Well, not quite.
The fact was that the Valkyrie was caught by the development of two new technologies — the surface-to-air missile and the intercontinental ballistic missile. The former made high-speed, high-altitude runs much more dangerous (although it should be noted that the SR-71 Blackbird operated very well in that profile). The latter offered a more rapid strike capability than the XB-70 and was cheaper.
Aviation historian Joe Baugher notes that as a result of the new technologies, the XB-70 was reduced by the Eisenhower Administration to a research and development project in December 1959. The B-70 was reinstated for production during the 1960 presidential campaign in an attempt to deflect criticism from John F. Kennedy. But Kennedy eventually threw it back to the lab.
Despite a public-relations effort by top Air Force brass, the B-70 remained an RD program with only two airframes built. A 1966 collision during a flight intended to generate photos to promote General Electric's engines destroyed one of them. The surviving airframe is displayed at the National Museum of the Air Force in Dayton, Ohio.
Take a look at this video from Curious Droid on the XB-70.