The US Navy's X-47B unmanned combat air vehicle (UCAV) has successfully conducted the first autonomous aerial refuelling (AAR).
The refuelling marks completion of the final test objective under the navy's Unmanned Combat Air System demonstration programme.
US Navy Unmanned Carrier Aviation programme manager captain Beau Duarte said: "The ability to autonomously transfer and receive fuel in flight will increase the range and flexibility of future unmanned aircraft platforms, ultimately extending carrier power projection.
"In manned platforms, aerial refuelling is a challenging manoeuvre because of the precision required by the pilot to engage the basket. Adding an autonomous functionality creates another layer of complexity."
During the test, the X-47B connected to an Omega K-707 tanker aircraft and received more than 4,000lb of fuel using the navy's probe-and-drogue method.
The aircraft exchanged refuelling messages with a government-designed Refuelling Interface System (RIS) aboard the tanker and autonomously manoeuvred its fixed refuelling probe into the tanker's drogue.
Commenting on the refuelling test, X-47B deputy programme manager Barbara Weathers said: "This segment of the X-47B demonstration programme allowed us to further mature AAR technologies and evaluate the government tanker RIS.
"We used similar command-control and navigation processes previously demonstrated during the X-47B landings aboard the aircraft carrier."
The US navy has accomplished several significant firsts with the X-47B over the last few years.
In August 2014, X-47B completed a series of tests, operating safely and seamlessly with manned F/A-18s, aboard the navy's fourth Nimitz-class aircraft carrier USS Theodore Roosevelt.
Image: An X-47B in flight near USS George H W Bush. Photo: courtesy of Official US Navy, photo by Erik Hildebrandt / Released.