Last Friday, an F/A-18 Super Hornet fighter jet flew behind another aircraft, dipped its wings a little as it adjusted its position, and then connected its probe with a hose trailing from the plane in front of it. It then received hundreds of pounds of fuel, all while traveling at an altitude of around 10,000 feet. While it’s common for military aircraft to refuel in the sky, up until now, the planes giving them a top-off have always had human pilots. What sets this moment apart is that the refueling aircraft was a drone called the MQ-25. While there were two people in the Super Hornet, the drone was unoccupied—an unmanned aerial vehicle that schlepps and delivers fuel.