Boeing is aiming for a window of between late August and the end of September to undertake the first flight of the 787 if it is to be sure of keeping to the May 2008 first delivery schedule.
Meanwhile, the airframer is playing down the impact of pressures on one of its key suppliers Vought Aircraft Industries on the 787's build schedule.
Boeing Commercial Airlines vice-president marketing Randy Tinseth says that final assembly of the first aircraft is proceeding on schedule to meet the 8 July roll-out schedule, and the first flight is expected "in late August or September".
Tinseth says that 787-8 number one "will fly when it's ready to fly", and has about the scope of about a month to get airborne without disrupting the flight-test schedule.
"We have until the end of September [to fly] and then we have to start looking at the flight-test window" to establish whether the May 2008 first delivery schedule to All Nippon Airways can be achieved, he says.
The airframer, which is aiming to deliver 112 787s during the first two full years of production (2008 and 2009), says that challenges faced by Vought are not affecting the 787's overall programme schedule.
A memo to Vought employees obtained by Seattle newspapers reveals the company has experienced "ongoing schedule slippage" in obtaining parts it is supposed to install before shipping fuselage sections to Boeing.
This comes after reports surfaced that the head of 787 operations at Vought, Ted Perdue, recently left the company.
"There have been no schedule changes. We're just managing [the issue] company-to-company," says Boeing. "What we're doing with Vought is the same thing we're doing with all our partnersimplementing contingency plans for travelled work."
Vought says the issues faced by the company "are typical" and that Boeing has plans in place "for all of this".
"The parts that were missing from our 787 aft barrels were identified well before we shipped them," says Vought, adding: "No piece gets delivered without Boeing accepting it."
Vought continues to face some supply challenges. "We are not alone. There is a worldwide shortage for different components," it says.