Boeing has completed the fuel system ground tests of the US Air Force KC-46 engineering and manufacturing design (EMD) programme at Paine Field, Washington.
During the test, a Boeing 767-2C tanker, called EMD-1, flew its first airworthiness flight installed with an aerial refuelling boom and wing air refuelling pods, Flightglobal reported.
According to Boeing KC-46 spokesman Chick Ramey, the latest test will support US Federal Aviation Administration type certification of the 767-2C.
Ramey was quoted as saying: "[The June 2 flight] really concludes the initial part of airworthiness testing, so now EMD-1 will go into planned ground testing and will do some FAA certification off the 767-2C fuel provisions.
"It will enter the next phase of airworthiness testing following this ground testing phase."
Boeing is planning to test four engineering and manufacturing development aircraft, such as two 767-2Cs and two KC-46As, this year. Boeing manufactures these four aircraft under a contract signed in 2011.
The first full-up KC-46A test aircraft, EMD-2, is expected to carry out its first flight in this summer. It is predicted that the company is will deliver the first 18 of 179 KC-46 aircraft to the air force by 2017.
Earlier this year, Boeing conducted a successful test flight of 767-2C freighter aircraft, in which the aircraft flew from Paine Field, Washington and landed at the Boeing field in Seattle after a successful flight for three hours and 32 minutes.