DARPA has made driods that can pilot a plane during air to air refueling. This occurs when the fuel planes refuels an airborne jet, in flight. Its a technique  thats difficult at best.
Theoretically, an unmanned craft with the ability to air to air refuel would only need to land for occassional craft maintenance

In the past 12 months the droid pilots have successfully done an air to air refueling 11 times without any human input. The jet used in testing was an F18. The android was able to connect to the refueling jet in the toughest of conditions.

Not aonly could the robot pilot connect and take fuel in turbulence but even did so as the tanker was in a turn.
Human pilots have followed tankers through turns, but never connected during one.