Boeing began final body join of the first 787-9 stretch derivative at its Everett, Wash, facility on May 30.

The 206-ft long variant is stretched 20-ft over the baseline 787-8 and will carry 290 passengers in a typical three-class configuration, or 40 additional passengers. The aircraft, which will enter service early in 2014 with launch customer Air New Zealand, is expected to begin its test campaign in the third quarter.

The first three aircraft are being assembled on a surge line established on the former 767 production line in Boeing’s 40-24 building. The company says this will allow “for smoother integration of the 787-9 into the production system while continuing to ramp up production across the 787 program.” The first aircraft, line number 126 or ZB001, is due to roll out around the end of July.

Compared to the 787-8, the -9 is extrended with two five-frame stretch sections on either side of the wing. The -9 is designed to fly up to 8,500 nm, or 300 nm further than the -8. Maximum takeoff weight (MTOW) is just over 50,000 lb. more for the stretch at 553,000 lb. Boeing has managed to keep the weight target fixed since the firm configuration freeze in 2010, before which the MTOW was around 545,000 lb. In addition, ZB001 is believed to have been completed slightly below the provisional empty weight goals.

The 787-9 is also the first airliner to incorporate a hybrid laminar flow control (HLFC) system in its baseline design. The system, which passively ingests air through the leading edge of the tail structure to maintain a smooth boundary layer, was developed to reduce the empennage drag of the 787-9, and is built into the vertical tail. Boeing adds that 20 airlines and leasing companies have ordered 355 787-9s to-date, representing 40% of the total 787 firm orderbook.