The U.S. Air Force is using business jets (the 44 ton BD 700) to act as communications relay stations over Afghanistan. Think of it as a very low orbit communications satellite. The BD 700 carries BACN (Battlefield Airborne Communications Node) equipment. This allows ground troops to not only talk to other father away (anywhere, in fact), but BACN can also enable ground troops to quickly connect with warplanes overhead. This is done with software that automatically transfers the data between the normally incompatible radio equipment. BACN also provides communications between aircraft.
The BD 700 can stay in the air for over ten hours per sortie and flies at 40,000 feet. The air force plans to install BACN in Global Hawk UAVs, which are large enough to carry the gear, and can fly at the same altitude.
BACN is not a new idea for the air force. Six years ago, realizing that every aerial battlefield in the past few decades has featured several KC-135 tankers circling, waiting to refuel a thirsty warplane, gave the tankers another job. By adding a few hundred pounds of electronics mounted on a cargo pallet, which KC-135s are equipped to handle, the tanker was turned into a node in an aerial communications network. This solves the problem of how to connect warplanes to the new battlefield Internet when those planes do not have satellite communications capability. The aircraft use line-of-sight communications, which cannot connect with any ground station or aircraft that is over the horizon or behind a mountain. The system, called ROBE (Roll-On Beyond-line-of-sight Enhancement), was particularly useful in a mountainous area like Afghanistan. After the first 20 ROBE units, costing about $900,000 each, entered service, an upgraded model was introduced three years ago. The Department of Defense and NATO have already developed standards (LINK 16) for the transfer of video, picture and data electronically between ground stations, aircraft and ships using radio or satellite communications networks.
KC-135s can't use BACN because they normally fly lower, at about 20,000 feet. By next year, the air force will receive two more BD 700s.