The aircraft was moved to the flight line, where teams are preparing it to fly later this summer.
At 20 ft (6 m) longer than the 787-8, the 787-9 will extend the 787 family in both capacity and range, carrying 40 more passengers an additional 300 nautical miles (555 km).
The second and third 787-9s are in assembly. First delivery to launch customer Air New Zealand is set for mid-2014.
At the Paris Air Show earlier this year, Boeing launched the 787-10 Dreamliner, the third and largest member of the 787 family.
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