[Source: Wikipedia, http://en.wikipedia.org/wiki/Northrop_Grumman_RQ-4_Global_Hawk
The Northrop Grumman (formerly Ryan Aeronautical) RQ-4 Global Hawk (known as Tier II+ during development) is an ... unmanned aerial vehicle (UAV) used by the United States Air Force and Navy as a surveillance aircraft.
In role and operational design, the Global Hawk is similar to the Lockheed U-2, the venerable 1950s spy plane. It is a theater commander's asset to provide a broad overview and systematic target surveillance. For this purpose, the Global Hawk is able to provide high resolution Synthetic Aperture Radar (SAR)—that can penetrate cloud-cover and sandstorms— and Electro-Optical/Infrared (EO/IR) imagery at long range with long loiter times over target areas. It can survey as much as 40,000 square miles (103,600 square kilometers) of terrain a day.