The high risk of using manned aircraft for reconnaissance over hostile territory was made clear by the downing of Gary Powers over the Soviet Union in 1960 and the death of a U-2 pilot during the Cuban missile crisis. To minimise this risk, Teledyne Ryan Aeronautical was called upon to modify its basic Firebee target to fly autonomous, pre-programmed, long-range reconnaissance missions. Twenty-eight special-purpose variants were developed to gather photographic, infrared and electronic intelligence information, to carry out electronic countermeasures, and to act as decoys in probing enemy defences.
During the Vietnam conflict, over a thousand Ryan unmanned aerial vehicles (UAVs) carried out 3,435 sorties on round-trip missions of up to 1,400 miles, sparing the lives of many pilots and freeing them for other missions. These vehicles were the forerunners of modern UAVs and in the ensuing years were followed by other TRA unmanned target and reconnaissance aircraft, including Compass Arrow, Compass Cope, Firebolt, the Scarab Model 324, Argus and the BQM-1 45A.
In May 1995 TRA was selected by the US Department of Defense to design and build the next generation, high-altitude-endurance unmanned aerial reconnaissance system, the Tier II Plus Global Hawk. At the roll-out ceremony of the Global Hawk on 20 February, 1997 Dr Paul G Kaminski, then the Under Secretary of Defense for Acquisition and Technology declared. "Global Hawk will be the vanguard of a new generation of unmanned aerial reconnaissance and surveillance vehicles. Global Hawk will help US forces and our allies achieve information well into the 21st century. It will provide what I call that highly desirable, unfair advantage for our forces."

Price is the driving force of the programme, the only firm requirement is a unit fly-away price of US$10 million per aircraft and performance is expressed in terms of well defined goals. Eliminating military specifications, computer-aided design and manufacturing, and the use of commercial off-the-shelf hardware enabled the first air vehicle to be completed in 27 months rather than the four years often required for a new programme.
Global Hawk has an unprecedented range of capabilities including long endurance, world wide connectivity, near-real-time imagery collection and all-weather sensors. Numerous capabilities also enhance its ability to survive proliferation threats anywhere in the world. Electronic support measures (ESM) onboard the aircraft include a threat-warning receiver, electronic countermeasures and towed decoys. Using an AFMSS-based automated mission planning system, the aircraft's flight profile can be adjusted automatically for threat avoidance. Survivability is enhanced further by operating at altitudes of up to 65,000 feet to minimise surface-to-air missile exposure, and by using in-theatre assets such as AWACS and ISTARS. Global Hawk specifications include an all-carbon fibre composite wing with a wingspan of 116.2 feet, a height of 15.2 feet and a gross take-off weight of 25,600lbs. Global Hawk's AC 3007H turbofan has been tested at altitudes up to 70,000 feet. The Tier II Plus concept of operations is highly flexible and has both range and endurance as variables. For example, with 42 hours of endurance and 14,000 miles of range, Global Hawk can travel 14 hours from its main operating base (MOB), remain on station at 65,000 fleet over a forward target area for 22 hours and then continue a further five hours to a forward operating base (FOB). From its FOB Global Hawk can travel back to its area of interest and remain on station for up to 31 hours before returning to the FOB. The launch and recovery element of the ground station, equipped with a differential global positioning system and located at the FOB, enables Global Hawk to take off and land automatically.
Near-real-time reconnaissance imagery is obtained by an integrated sensor system consisting of an all-weather synthetic aperture radar/moving target indicator (SARIMTI), a high-resolution electro-optical digital camera and a third-generation infrared sensor that all operate through a common signal processor that is the equivalent of an airborne super computer. The sensor system makes it possible to distinguish types of vehicle, aircraft and missile and it can look through adverse weather, day or night. It can search a 40,000-square- nautical-mile area in 24 hours with three-foot resolution, or search 1,900-two-kilometre-square spots with one-foot resolution.
The superior performance of the Tier II Plus Global Hawk system will enhance the US military's ability to prevail in all types of operation, from peacekeeping missions to combat.