With the first set of Pratt & Whitney engines delivered for the U.S. Air Force’s KC-46 test aircraft, Boeing is planning to roll out the first green 767-2C next year.

The 767-2C is the customized commercial platform on which the KC-46 is designed. The 2C includes provisions — such as customized plumbing — to support the KC-46’s refueling mission.

Pratt & Whitney delivered the first two PW4062 engines during a ceremony at Boeing’s Everett, Wash., facility. These engines, each providing 62,000 lb. of thrust, will power the first of four test articles paid for by the U.S. Air Force. This engine also is used on commercial 767s, MD-11s and early 747 models.

Boeing won a contract worth $4.9 billion in February 2011; it includes delivery of 18 KC-46s in 2017. These are the first of an anticipated buy of 179 tankers to begin replacing the aging KC-135 fleet.

The KC-46 program is among the Air Force’s top three procurement priorities alongside the single-engine, stealthy F-35 and a new long-range bomber.

The Air Force completed the KC-46 critical design review in August, one month ahead of plan.

The 767-2C is slated to begin flying by June and the KC-46 is slated to start flight testing in January 2015. Boeing has fabricated the first KC-46 refueling boom.

It remains to be seen how much the KC-46 program will cost Boeing. The government estimates the cost at completion is $5.6 billion, $500 million more than Boeing’s estimate and $700 million more than the Air Force’s contract ceiling. Because the contract is fixed price, any overrun must be paid for by Boeing.