SR-72
I very much doubt this hypersonic aircraft will fly in the timescale suggested by Lockheed.
I suspect that for many years the USAF have been using a number of very stealthy, high-altitude, long endurance UAVs to provide coverage of denied areas. The RQ-170 was an old low-tech UAV that had been in use for a number of years. I think it may have been deliberately crashed in Iran in the hope that, whilst they were examining the on-board software, a hidden virus would find its way onto Iranian systems and eventually bugger up their nuclear programme.
Heimdall