The U.S. Missile Defense Agency plans to send an unmanned aircraft into the stratosphere sometime in 2020-2021 and attempt to shot down a ballistic missile in its boost-phase using an electrical laser. Lockheed Martin says a unmanned version of the U-2 might be a suitable platform for that.
By U.S. Air Force photo by Master Sgt. Rose Reynolds [Public domain], via Wikimedia Commons
The aircraft has the necessary electrical power output and includes an open mission system architecture to plug in new technologies.
However, converting the aircraft to fly without a pilot requires significant changes to the flight controls.