With its debut at the 2010 Farnborough air show days away, Boeing has issued a "cautionary note" that the first 787 delivery could slip into early 2011, citing slower than anticipated instrumentation configuration changes and inspections of the horizontal stabiliser.
Boeing vice president and general manager Scott Fancher says some of the recent issues have "stacked up" and "could see [first delivery] move a few weeks into the new year".
Fancher says the schedule has not officially slipped beyond the fourth quarter timeframe to early to 2011, but adds the airframer will provide more information "as we get closer to the conclusion of flight test".
"None of the issues have to do with airplane performance," says Fancher, who emphasises the aircraft continue to perform as expected, adding the fleet of five flying 787 test aircraft has accumulated more than 1,100h of flight testing over 365 flights.
Boeing aims to complete 2,400h of flight testing on its four Rolls-Royce Trent 1000 powered test aircraft.
Fancher declined to say which instrumentation configuration changes had slowed the flight test programme that began in December 2009, though preparation for flight test aircraft ZA004's flight loads survey and returning ZA001, which last flew on 12 June, to flight testing, are believed to have taken significantly longer than first planned.
"We'll do one block of testing with one [instrumentation] configuration, then change," says Fancher who adds the changes have "taken a bit longer than first planned".
Additionally, Fancher says that inspections of the horizontal stabilisers of the test fleet are now complete, but that process has "led to a little bit of schedule pressure".
Following the revelation of the workmanship issue on 24 June that prompted the inspections, Boeing insisted the "issue will be addressed within the existing programme schedule," though that expectation appears to have shifted.
As a result, first flight of the sixth flight test aircraft, ZA006, the second General Electric GEnx-1B powered 787, has slid to August, says Fancher.
Boeing confirms ZA003, which will represent the company at the Farnborough air show, and ZA001, have both required re-work of their horizontal stabilisers.
In April a source at launch customer ANA indicated the carrier anticipated a slide in the schedule that could result in an early 2011 delivery.