The Pathfinder was modified in 1998 into the longer-winged Pathfinder-Plus configuration. It included a new wing section which increased the overall wingspan from 98.4 feet (30.0 m) to 121 feet (36.9 m). The new center section was topped by more-efficient silicon solar cells which could convert almost 19 percent of the solar energy they receive to useful electrical energy to power the craft's motors, avionics and communication systems. Maximum potential power was boosted to about 12,500 watts on Pathfinder-Plus. The number of electric motors was increased to eight. The Pathfinder-Plus flights in 1998 validated power, aerodynamic, and systems technologies. On August 6, 1998, Pathfinder-Plus raised the national altitude record to 80,201 feet (24,445 m) for solar-powered and propeller-driven aircraft.

The Helios incorporated a fuel cell energy storage system to provide power for flying through the night, making it capable of continuous flight at 50,000 - 70,000 feet for months at a time. Helios was expected to be widely deployed as broadband communications platforms, providing cost-effective complements to satellite and terrestrial communication systems. On June 26, 2003, the Helios Prototype broke up and fell into the Pacific Ocean west of the Hawaiian Island Kauai during a systems checkout flight.  The program was subsequently ended by NASA.

The Lockheed Martin / Boeing DarkStar was one of three high-tech, stealth surveillance UAVs underway in the late-1990s as part of a U.S. Defense Advanced Research Projects Agency (DARPA) effort to produce new UAVs by 2015. DarkStar had a length of 15 ft., and a wingspan of 60 ft. On March 29, 1996, DarkStar made its first flight, reaching an altitude of 5,000 feet and successfully executed a fully automated flight from takeoff to landing using GPS. It operated at ranges greater than 500 nautical miles and was able to stay on station for more than eight hours at altitudes greater than 45,000 feet. In 1999 the Defense Department terminated the DarkStar program.

The Aerosonde is a small UAV designed to collect weather data over oceans and remote areas. The Aerosonde was developed by Insitu, and is now manufactured by Aerosonde Ltd. The Aerosonde carries onboard a small computer, meteorological instruments, and a GPS receiver for navigation. On August 21, 1998, an Aerosonde completed a 2,031 mile (3,270 km) flight across the Atlantic Ocean at an altitude of 5,500 ft (1,680 meters), and was the first UAV crossing of the Atlantic Ocean and also the smallest aircraft ever to cross the Atlantic. Aerosondes have also been the first unmanned aircraft to penetrate tropical cyclones, during missions in 2001 and 2005.

The Reaper is employed primarily as an intelligence-collection asset and secondarily against dynamic execution targets. Given its significant loiter time, wide-range sensors, multi-mode communications suite, and precision weapons, it provides a unique capability to perform strike, coordination, and reconnaissance against high-value, fleeting, and time-sensitive targets.

Reapers can also perform the following missions and tasks: intelligence, surveillance and reconnaissance, close air support, combat search and rescue, precision strike, buddy-lase, convoy and raid overwatch, route clearance, target development, and terminal air guidance. The MQ-9's capabilities make it uniquely qualified to conduct irregular warfare operations in support of combatant commander objectives.

The Northrop Grumman RQ-4 Global Hawk is a surveillance aircraft, similar in role to the manned Lockheed TR-1 spy plane. The Global Hawk can collect high resolution Synthetic Aperture Radar (SAR) and Electro-Optical/Infrared (EO/IR) sensor imagery at long range with long loiter times over target areas.  The Global Hawk costs about $35 million USD (actual per-aircraft costs; with development costs also included, the per-aircraft cost rises to $123.2 million USD each). The GH has a 116-foot wingspan, can sustain flight operations for up to 32 hours, allowing it to fly autonomously, collect and transmit surveillance data at 65,000 feet, and then return to its base without refueling.