A Boeing (BA -0.20%) prototype unmanned aerial tanker drone has successfully refueled a Navy fighter plane, a huge milestone for a program that could be worth as much as $10 billion for the aerospace contractor.

In 2018 Boeing was awarded an initial $805 million to design and develop the MQ-25 Stringray drone as a tanker. The Navy envisions stationing the drones on aircraft carriers, amplifying the carrier air wing's effective strike range by up to 400 nautical miles. But the contract was speculative, at best, and subject to Boeing and the Pentagon working out all the potential kinks to make the unmanned option a reality.

Aerial view of the Stingray connecting with an F-18 Hornet to transfer fuel.

Boeing's Stingray drone transfers fuel during the June 4 test. Image source: Boeing.

Boeing said that during a June 4 test flight the MQ-25 successfully extended its hose and transferred fuel to a U.S. Navy F/A-18 Super Hornet, demonstrating precision deployment and ample stability in completing a mission that required the two planes to fly within 20 feet of each other.

"This history-making event is a credit to our joint Boeing and Navy team that is all-in on delivering MQ-25's critical aerial refueling capability to the fleet as soon as possible," Leanne Caret, CEO of Boeing's defense unit, said in a statement. "Their work is the driving force behind the safe and secure integration of unmanned systems in the immediate future of defense operations."

The successful demonstration likely bodes well for the program. The Navy sees drone refueling as a way to cut down on the expense and wear and tear on its existing refueling fleet. As of 2018, the Navy's Hornet fleet did most of the refueling work, with upward of 30% of Navy Hornets devoted to aerial refueling at any given time.