Three years after the U.S. Defense Advanced Research Projects Agency (DARPA) and NASA successfully tested a robotic in-flight refueling system, both the air force and navy are now developing systems of their own. Each service uses a different in-flight refueling system, and both are going to use the automated refueling systems to ease the workload of the manned aircraft giving, or getting, fuel. The original DARPA test has an F-18 fighter, modified to operate without a pilot, equipped with new refueling software and hardware, that was able to successfully refuel in the air. The new air force and navy systems are going to use UAVs (an air force X-45C, and a navy X-47B) to get refueled. With this capability, a UAV can stay in the air longer, and no longer have to spend several hours returning to base, landing, refueling, and taking off and returning to its patrol area.
Both services will used manned aircraft, but under control of the automatic refueling software, to test the systems, before using the UAVs. The navy will use an F-18 as a surrogate UAV first. The air force will use a Learjet, then an F-16 as surrogates, before they use the UAV.
For several decades, old fighters have been rigged with remote control capability, so they can be flown without pilots. This way, the old aircraft can be used as targets for air-to-air, or ground-to-air missiles. As far back as the 1970s, such robotic fighters were even successfully used in tests of air-to-air combat operations. All this experience has been used in developing a new generation of robotic combat aircraft. Actually, the first generation of such aircraft will be remotely controlled from the ground, or another aircraft, most of the time. This is possible now because of improvements in communications (especially via satellite links) and sensors (cameras and radars) to give the remote pilots a better sense of where they are. This "situational awareness" is essential for air combat. It is not as essential for delivering the current generation of smart bombs (especially the GPS guided bombs.) Thus UAVs are already being used for bombing missions.
But new advances in flight control software, and sensors (more of them, cheaper and with better capabilities), make it possible to build robotic fighters, and bombers that can operate by themselves. Such capabilities already exist, as current flight control software will act to protect the aircraft if communications is lost with the human controller. Actually, robotic bombers have been around for half a century, they're called cruise missiles. Before the Tomahawk was developed, the navy had several pilotless aircraft designed to deliver nuclear weapons all by themselves. But the new generation of robotic (as opposed to remotely controlled) bombers will receive their orders, and then be sent off to do the job (with a human flight commander observing it all remotely, ready to abort anything not going according to plan.
The in-flight refueling is necessary because unmanned, as well as manned, aircraft can carry more weapons if they can refuel during the mission. For UAVs, such refueling enables these aircraft to stay in the air for days at a time. That's what UAVs are built for. Since fighter pilots have to sleep, and their aircraft are not built for round-the-clock missions, UAVs have a major edge.