The US Air Force (USAF) has completed a fuel transfer from a KC-46A Pegasus tanker to F-16 Fighting Falcon and C-17 Globemaster III aircraft.

The in-flight refuelling was conducted as part of a test to ensure that the hydraulic pressure relief valves are installed to correct higher-than-expected axial loads in the KC-46A boom.

During testing, Boeing’s hardware solution was found to alleviate the problem associated with the boom axial loads.

USAF Secretary Deborah Lee James said: "I'm encouraged by these results.

"The KC-46 programme continues to move forward, making important progress that will get this vital capability into the hands of the warfighter."

These tests with the F-16 and C-17 are in line with the milestone C requirements to rendezvous, contact and transfer fuel to several receiver aircraft types.

"The KC-46 programme continues to move forward, making important progress that will get this vital capability into the hands of the warfighter.”

The final milestone C flight test to transfer fuel through the fixed boom to an A-10 Thunderbolt II is expected to take place later this month.

USAF acquisition principal deputy assistant secretary Darlene Costello said: "Once complete with the A-10, we will request approval from Mr. Frank Kendall, undersecretary of defence for acquisition, technology and logistics, to award production Lots 1 and 2, totalling 19 KC-46A aircraft.”

The 50.4m-long multirole tanker is powered by two Pratt & Whitney PW 4062 engines to refuel all US, allied and coalition military aircraft compatible with international aerial refuelling procedures.

Designed to carry passengers, cargo and patients, the Boeing-built aircraft can detect, avoid, defeat and survive threats using multiple layers of protection.

Image: A KC-46A prototype during a test flight. Photo: courtesy of Ken Fielding.