Boeing is preparing the first 787-9 for initial ground tests following a low-key rollout event at the company’s Everett, Wash., facility on Aug. 24.

The aircraft, a 20-ft. stretch derivative of the baseline 787-8, is scheduled to undergo fuel system checks in coming days and conduct initial engine checks as early as next week. Assuming no issues are discovered during system activation and initial ‘gauntlet’ testing, taxi tests and first flight are likely to take place around mid-September. The first 787-9 is scheduled to be delivered to launch customer Air New Zealand in mid-2014.

Boeing is allocating three dedicated test aircraft to a certification and test effort that will take approximately six months, and will introduce a fourth fully configured aircraft late in the program for function and reliability work. The first aircraft, ZB001, is the 126th 787 to roll off the combined Everett and Charleston, S.C., production lines. Boeing says the second and third 787-9s, ZB002 and ZB021, are already in final assembly.

After the extreme challenges and delays encountered with the 787-8, the pressure is on Boeing to ensure the 787-9 flight test effort goes far more smoothly. However, despite the ambitious requirements of the design – which is configured to carry 40 more passengers and fly 300nm further than the 787-8 – Boeing appears quietly confident in meeting performance guarantees as well as program schedule. Compared to the 787-8, the -9 is extended with two five-frame stretch sections on either side of the wing. Maximum takeoff weight (MTOW) is 553,000 lb., or just over 50,000 lb. more than the baseline -8, while empty weight is reportedly as much as 2% less than specification.

Boeing currently holds 376 orders for the 787-9, or 40% of the total 787 firm orderbook of 936. The balance is made up of 510 787-8s and 50 of the recently-launched 787-10 ‘double-stretch’ derivative.