SEATTLE — Boeing showed off the interior of a 787 Dreamliner parked at Paine Field earlier this week, and provided a glimpse of some advances on the 787 assembly line inside the factory.

The partial passenger cabin, installed in Dreamliner No. 3, will be used to test elements of the passenger experience, including air flow, noise levels and the heating and emergency oxygen systems. Meals will be prepared in the galley. Toilets will be stress-tested.

But the interior proved disappointingly less opulent than the previous 787 cabin mock-ups Boeing has shown, which featured airy, light-filled entrance lobbies.

In this plane, reporters entering from a stairway immediately faced two side-by-side galleys with a narrow alley in between — just as one might on an airliner today.

Certainly the new windows are a big improvement over those typical on today's airliners. They are tall enough to allow a seated passenger to look out and up without bending down. Pushing a button dimmed the windows electrically from clear to dark.

But the basic economy seats provided no more legroom than usual. The overhead stow bins are designed to give extra headroom, but a 6-foot-tall passenger in the window seat must still duck to the side to stand up.

Still, it's a test interior, not one installed for a customer.

The airlines decide the positioning of galleys and the seat legroom. Boeing director Blake Emery described the galleys blocking the entrance as a "worst-case scenario" of airline choices.

Meanwhile, the assembly-line tour did indicate progress in the manufacturing process.

Suppliers are sending more complete airplane sections to Everett, Wash. One visible change: While the central-fuselage sections of Dreamliners 13 and 14 are unpainted, with their composite material protected only by a greenish-hued coating, the two behind them arrived from Charleston, S.C., already painted white.

In similar fashion, said spokeswoman Mary Hanson, Dreamliner No. 16 is the first to arrive complete with the modification needed to fix a flaw at the wing/body join. The earlier Dreamliners had to be modified in Everett.

The assembly line is much less cluttered with scaffolding than it was late last year, though some scaffolding lingers — underneath a wing on one jet, under the horizontal tail of another — where mechanics are reworking parts of planes rather than just snapping the parts together.

The tour revealed that launch airline All Nippon Airways of Japan is taking 10 of the first 13 Dreamliners destined for customers.

A dozen complete airplanes have been rolled out onto Paine Field so far, in addition to two ground-test 787s that will never fly.

Of the dozen that will, the first three are so heavily modified that they are designated for test only.

Six of the remaining nine so far built will go to ANA. And inside the factory, the four airplanes being assembled also have ANA tail markings.

Most of those airplanes are known to be heavier than later planes will be and required extensive rework because of earlier assembly mistakes.

Dreamliner No. 3 is due to begin flight tests later this month, fitted front and rear with passenger seats, galleys, lavatories and crew rests. The central part of the cabin is reserved for computer stations that engineers will use to monitor systems in flight.

Flight-test engineer Derek Muncy described some of the tests ahead on his plane.

He said Boeing this week will deploy the doorway evacuation slides. The exterior of the airplane's doors are temporarily framed with bright orange padding to protect the airframe in case the slides malfunction.

Several of the in-flight tests require Boeing to fill all 135 passenger seats on the plane. Meals will be cooked on board, and bottles of soda and water refrigerated.

In the crew rest area, there's an evacuation test requiring a small person to pull a larger person through the escape hatch.

In another test, smoke generators will simulate fires in different areas to see that smoke doesn't seep between floors.

The air flow must be sufficient to draw out enough smoke so that a person unfamiliar with the airplane has enough time to find the simulated fire.

Clearly, safety is a big a part of the testing. As for judging comfort on the Dreamliner, that may have to wait until a 787 flies scheduled passengers.