If you thought an aerial tanker's "flying boom" was rigid, you better watch this video
Used as the standard aerial refueling system for U.S. Air Force fixed-wing aircraft the flying boom is a rigid, telescoping tube, maneuvered by a “boom operator” by means of a control stick.
This method has the advantage to eliminate the requirement for the receiver pilot to plug the probe into the hose’s drogue: once the aircraft has reached the refueling position the operator moves the boom to insert the tube in the receptacle of the receiver aircraft.
The following video shows the boom’s maneuverability: it can be moved quite quickly to follow the receiving plane and prevent it from disconnecting during refueling.
Both the KC-135 and the KC-10 tankers have a single boom that can be can be equipped with an adapter for probe-equipped aircraft and can refuel one receiver at a time. The KC-135 replacement plane, the future KC-46 based on the KC-767, will be fitted with a single boom and two hoses to refuel also aircraft using the probe and drogue mechanism.
Image credit: U.S. Air Force