The Northrop Grumman RQ-4 Global Hawk is a high-altitude, remotely-piloted surveillance aircraft of the 1990s–2020s. It was initially designed by Ryan Aeronautical (now part of Northrop Grumman), and known as Tier II+ during development. The RQ-4 provides a broad overview and systematic surveillance using high-resolution synthetic aperture radar (SAR) and electro-optical/infrared (EO/IR) sensors with long loiter times over target areas. It can survey as much as of terrain per day, an area the size of South Korea or Iceland. The Global Hawk is operated by the United States Air Force (USAF). It is used as a high-altitude long endurance (HALE) platform covering the spectrum of intelligence collection capability to support forces in worldwide military operations. According to the USAF, the superior surveillance capabilities of the aircraft allow more precise weapons targeting and better protection of friendly forces. Cost overruns led to the original plan to acquire 63 aircraft being cut to 45, and to a 2013 proposal to mothball the 21 Block 30 signals intelligence variants. The initial flyaway cost of each of the first 10 aircraft was US$10 million in 1994. By 2001, this had risen to US$60.9 million, and then to $131.4 million (flyaway cost) in 2013. The U.S. Navy has developed the Global Hawk into the MQ-4C Triton maritime surveillance platform. As of 2022, the U.S. Air Force plans to retire its Global Hawks in 2027. Development Origins In the 1990s, the Air Force was developing uncrewed aerial intelligence platforms. One was the stealthy Lockheed Martin RQ-3 DarkStar; another was the Global Hawk. Due to budget cuts, only one of the programs could survive. It was decided to proceed with the Global Hawk for its range and payload rather than go with the stealth Dark Star. The Global Hawk took its first flight on 28 February 1998. The first seven aircraft were built under the Advanced Concept Technology Demonstration (ACTD) program, sponsored by DARPA, in order to evaluate the design and demonstrate its capabilities. Demand for the RQ-4's abilities was high in the Middle East; thus, the prototype aircraft were actively operated by the USAF in the War in Afghanistan. In an unusual move, the aircraft entered initial low-rate production while still in engineering and manufacturing development. Nine production Block 10 aircraft, sometimes referred to as RQ-4A, were produced; of these, two were sold to the US Navy and an additional two were deployed to Iraq to