Boeing workers in Everett loaded the first wing spar for the first U.S. Air Force KC-46A aerial refueling tanker, starting production of that aircraft and achieving another milestone toward delivering 179 tankers during the next 14 years.

The KC-46A is based on the commercial 767-200ER, a proven airframe in service as an airliner, freighter and tanker. Boeing has delivered more than 1,050 767s worldwide.

“The Air Force is really excited and pleased that our No. 1 modernization priority has begun fabrication and entered the factory at Everett. The Boeing team continues to make significant progress in the KC-46 development program,” said Major General John Thompson, U.S. Air Force Program Executive Officer for Tankers.

The spar, the main structural component of the wing, is 82 feet 5 inches long. On the aircraft, it provides critical support for flight loads and the weight of the wings when the plane is not flying.

The program’s next major contractual milestone, the Air Force’s Critical Design Review, starts next month.

“We are building on the strong partnership that the Air Force and Boeing have developed during the past two years,” said Maureen Dougherty, Boeing Vice President and KC-46 Tanker Program Manager.

“From the enhanced flight deck to the modernized boom, our tanker will provide unequaled capabilities that will allow it to offload more fuel and carry more passengers, cargo and medical patients,” she added.

Boeing employees are also preparing the 767 production line for assembly of the next-generation tanker’s aft and forward body structures. The aircraft will be assembled in November and roll out of the factory in January.

“We’re proud to support the U.S. Air Force with a production line that emphasizes quality, efficiency and safety,” added Scott Campbell, Vice President and General Manager, 767 Program, Boeing Commercial Airplanes.

Next June, Boeing will begin installation of military-unique systems on the aircraft at Boeing Field in Seattle as well as testing. First flight for the fully provisioned tanker is scheduled for early 2015, with first delivery in 2016.

Boeing expects to build and deliver the first 18 KC-46As by 2017 and a total of 179 by 2027 if all options under the contract are exercised.