This week, "Salty Dog 502"—one of the Navy's two X-47B carrier based unmanned aircraft— did something no other drone has ever done: it lined itself up behind a human-flown tanker plane and pulled up for a fill-up. While the technology used for the refueling had been previously tested and demonstrated on a manned Learjet acting as an "unmanned aircraft surrogate testbed", this was the first time that a drone had completely autonomously flown in behind a tanker plane and completed an actual refueling. In-flight refueling extends the range of military aircraft, allowing them to stay in the air longer while on patrol and fly extended long-range missions.