Boeing didn't take an extra day off for the Fourth of July. The aircraft manufacturing company officially began assembling its first KC-46 tanker today. Workers loaded the first wing spar for the plane, a small but important first step towards producing a complete KC-46.

Daryl Mayer, a journalist with the 88th Air Base Wing Public Affairs office, has some background.

Boeing's announcement this past week that they have begun assembly of the first KC-46 wing spar is a significant event for the Air Force tanker program. It marks the start of assembly of the first KC-46 Engineering and Manufacturing Development aircraft.

"We are excited and pleased that KC-46 fabrication has begun. The Boeing team continues to make significant progress in the development of the Air Force's next tanker," said Maj. Gen. John Thompson, Program Executive Officer for Tankers at the Air Force Life Cycle Management Center. "The development effort is on track, detailed test planning is making good progress, and initial beddown, training and sustainment planning is underway."

The Air Force is about a third of the way into the KC-46 tanker development program. The Air Force contracted with Boeing in February 2011 to acquire 179 KC-46 Tankers to begin recapitalizing the more than 50-year-old KC-135 fleet. The initial delivery target is for 18 tankers by 2017. Production will then ramp up to deliver all 179 tankers by 2028.

The aircraft being produced at the Boeing factory in Everett, Wash., is a commercial derivative design based on the Boeing 767-200ER passenger aircraft. When the aircraft comes off the Everett production line, it will be a 767-2C Provisioned Freighter that will eventually become a military-configured KC-46 tanker.

The first fully equipped KC-46 is slated to fly in early 2015.