Boeing and the U.S. Air Force have for the first time flown a prototype aircraft in the KC-46 Pegasus development program.

The aircraft flown in the engineering, manufacturing and development phase of the program was a modified 767-2C freighter, upon which the aerial refueler will be based.

"Getting in the air is a critical step in the development of this important capability for the warfighter," said Brig. Gen. Duke Z. Richardson, the program executive officer for tankers at the Air Force Life Cycle Management Center. "The team at Boeing has done a remarkable job creating an entirely new aircraft that will soon become the backbone of our ability to project power anywhere in the world."

The modified 767-2C will be outfitted with a refueling boom and other military specific equipment and systems following certification.

The KC-46 is to replace the Air Force's fleet of aging KC-135s. Boeing won the contract for the aircraft in 2011 and is to deliver 18 KC-46 aircraft -- plus support equipment -- August 2017.

The Air Force plans to acquire 179 of the planes.

"Today's (Sunday's) flight is a key step in the next generation of tankers," said Col. Christopher Coombs, the KC-46 system program manager. "We know flight testing will lead to some discovery; today's flight kick-starts that work.

"There is an aggressive schedule going forward into the Milestone C decision point for approval to start Low Rate Initial Production, but we remain cautiously optimistic we can meet the mark."