A high-flying unpiloted solar-electric aircraft has doubled as a giant telecommunications tower. From an altitude far above Earth, the craft transmitted hours of next-generation mobile voice, data, and video services to handheld devices on the ground.

Aerial platforms, in some cases, may grab market share from telecommunications satellites in the future.

The recently concluded tests were conducted over Kauai, the northernmost island of the main Hawaiian Islands. Winging its way far above the Pacific Ocean, the Pathfinder-Plus, an aerial automaton built by AeroVironment, Inc., is pioneering new ways to handle ever-growing terrestrial telecommunications needs.

Pathfinder-Plus cruised to over 65,000 feet (19,812 meters) altitude, positioning itself above the weather and commercial air traffic. At that height, the airborne platform doubled as a 12-mile (19-kilometer) high tower.

During the tests, the world's first digital high definition television (HDTV) broadcast transmission from the stratosphere yielded a picture-perfect video signal to a fixed receiver on the ground. That signal achieved twice the resolution of conventional broadcast transmissions, SkyTower officials said.

SkyTower platforms are touted as a way to fill in "urban canyons" - coverage areas missed by terrestrial and satellite broadcast transmissions due to tall buildings, terrain, and other obstacles, doing so using a fraction of the power.

"We see SkyTower platforms as an excellent complement to satellite systems," said Stuart Hindle, Vice President of Strategy & Business Development for SkyTower. "Satellites excel at ubiquitous coverage and connectivity of remote users. SkyTower platforms excel at low cost, high bandwidth coverage within local access markets," he told SPACE.com.

Hindle said aerial platforms operating at stratospheric heights, contrasted to Earth orbiting spacecraft, are capable of achieving tremendously higher levels of frequency use than satellites.

For instance, Hindle added, a single SkyTower platform can provide over 1,000 times the fixed broadband local access capacity of a geostationary satellite using the same frequency band, on a bytes per second per square mile basis.

"Additionally, multiple platforms can serve the same area due to spatial diversity, further reusing the spectrum. This high spectral efficiency makes the platform very cost-effective," Hindle said. To deploy the system, it is a fraction of the cost of satellite and terrestrial systems -- such as cable and DSL -- on a dollar/subscriber basis, including redundant back-up systems, he said.

"SkyTower platforms are basically geostationary satellites without the time delay," Hindle said. Floating in the stratosphere, he said, the platforms have the added feature that they can be brought down at will for servicing and upgraded with the latest technology.

Small, low-cost, stationary user antennas can be utilized due to the tight turning radius of the aircraft, which makes it appear geostationary from the ground.

SkyTower plans to launch the first commercial service within three years. The plan is to provide fixed wireless broadband infrastructure, with the firm already having "advanced discussions" with several domestic and international service providers interested in the airborne technology.

The Pathfinder-Plus sports a 121-foot (37-meter) wingspan. It is a smaller version of AeroVironment's Helios aircraft that, during NASA testing in Hawaii last summer, broke the world altitude record for non-rocket powered aircraft.

Next year, Helios is being geared to use the world's first fuel cell based aircraft energy system. That enables the vehicle to operate through the night. Production versions of Helios unmanned aerial vehicles (UAVs) using the new energy system are expected to fly up to six months or more between landings.

AeroVironment formed SkyTower two years ago in pursuit of a commercial telecom business that can benefit by adopting the solar-electric aircraft concept. Aerial platforms are of interest to the government too, ranging from battlefield communications to emergency backup telecom services.

In September, NASA plans to use the Pathfinder-Plus aircraft to carry out an Earth remote sensing campaign.

The craft will be loaded with multi-spectral imaging hardware. From high altitude, the platform will assess several factors. These include how crop yields might be increased given best time to harvest; monitoring changes in irrigation levels; and spotting outbreaks of crop disease.