Aircraft maker Boeing has begun assembly of the first of a new generation of the company’s iconic 737 passenger aircraft.

A few days ago, workers at the company’s Renton, Washington, plant fashioned the wings for the maiden 737 MAX flight test aircraft. The wings are the first 737 components to be assembled in the Renton production process.

Machine operators loaded 737 MAX wing skin panels and stringers into the new panel assembly line that uses automation to drill holes and install fasteners in the upper and lower wing panels. Mechanics also loaded the initial parts of the aircraft’s first spars—internal support structures in wings—into fully-automated spar assembly machines.

The unfinished skins, stringers and spars are machined at the company’s skin and spar fabrication facilities and, when finished, are transformed into completed wings. The wings will be attached to the first 737 MAX fuselage on the new central final assembly line in Renton later this year.

“While the Renton factory continues to build at a rate of 42 airplanes a month, the new production line will allow the team to isolate the first 737 MAX build from the rest of production in order to learn and perfect the build process,” Boeing says.

The 737 MAX “incorporates the latest technology including CFM International LEAP-1B engines, advanced technology winglets and other improvements to deliver the highest efficiency, reliability and passenger comfort in the single-aisle market” adds the company.

Beginning in 2017, the new single-aisle airplane, “will deliver 20 percent lower fuel use than the first Next-Generation 737s and the lowest operating costs in its class—eight percent less per seat than its nearest competitor.”

The plane’s flight deck includes technologies showing the current and predicted flight path of the aircraft and potential conflicts with the terrain, as well as a heads-up display to provide flight and safety information at eye level.

BOEING 737 IS THE BEST SELLING JET LINER IN AVIATION HISTORY

Boeing began taking orders for the 737 MAX in 2011 and, to date, has more than 2,700,737 orders on the books for the new aircraft from 57 international and domestic airlines including Virgin Australia, Norwegian Air Shuttle, RyanAir, Alaska Airlines, Aeromexico, Air Canada, Turkish Airlines, Garuda Indonesia, Southwest Airlines, United Airlines, as well as a single unidentified “VIP” customer.

A basic 737 MAX liner carries a $78.3 million price tag. The cost per aircraft can climb to as high as $113 million for the high-end 737 MAX 9.

The Boeing 737 series is the best-selling jet airliner in the history of commercial aviation with the aircraft and its numerous variants continuously manufactured by the company since 1967. The very first 737 was ordered by Germany’s Lufthansa and entered service the following year.