Boeing's 787-10 is at least four years away from making its debut with launch customer Singapore Airlines in 2018, but the super-stretched Dreamliner is already undergoing flight tests – well, of a sort.

The 787-9 test plane which spent last week undergoing heat tests in the centre of Australia also managed to perform a series of evaluations germane to its big brother, even though the -10 is still on the drawing board.

Photo gallery: Inside the Boeing 787-9 test aircraft

We're actually picking up some -10 testing on this configuration" explains Dominic Thacker, the 787-9’s Lead Flight Test Engineer.

"Some of the systems will be similar, this being a type derivative" Thacker tells Australian Business Traveller. "It's scaled up so we're looking at a couple of things like environmental-specific testing.

"If we can do some of those tests in advance on a similar airplane it helps us downstream and will save us time later."

Variations of an airplane's base model are faster to be declared airworthy because they represent only a relatively small number of changes to the original design.

“Being a derivative of the -8 there are standard tests that we need to do, but because a lot of the testing we actually did previously on the -8, this is just a subset of what a major model needs to go through” explains Ryan Smith, Boeing's Test Operations Manager for the 787-9 program.

"We've flown the -9 into testing very very quickly" Smith says, noting the 787-9's maiden flight took place on September 17 2013, just 10 months before the first commercial model is due to be handed over to Air New Zealand.

Read: Air New Zealand gears up for Boeing 787-9 Dreamliner’s debut

At 68 metres (224 feet) from tip to tail, the Boeing 787-10 will be just five metres longer than the 787-9 and 11 metres more than the original 787-8 Dreamliner.

And while it won't be able to fly as far as the 787-9 or even the 787-8, Boeing sees the 787-10 as being all about maximising bums on seats.

The 787-10 is expected to seat 330 passengers in a standard three-class configuration, although that count could nudge 350 – after all, Boeing describes the 787-9 as accommodating "250–290 passengers in three classes" yet Air New Zealand has 302 seats in its own three-class configuration.

Singapore Airlines and Etihad Airways have inked orders for 30 Boeing 787-10s each, at a list price of US$289 million, with United Airlines putting up its hand for 20 more and BA a further 12.

Also read: Step inside Boeing’s 787-9 Dreamliner ZB002 with our exclusive photo-tour

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