The Northrop Grumman RQ-4 Global Hawk is an unmanned (UAV) surveillance aircraft. It was initially designed by Ryan Aeronautical (now part of Northrop Grumman), and known as Tier II+ during development. The Global Hawk performs a similar role as the Lockheed U-2. The RQ-4 provides a broad overview and systematic surveillance using high-resolution synthetic aperture radar (SAR) and long-range electro-optical/infrared (EO/IR) sensors with long loiter times over target areas. It can survey as much as 40,000 square miles (100,000 km2) of terrain a day.