It is a beautiful airplane, mid-sized with modishly thin wings that sweep back from the fuselage and tilt upward at the tips. Sitting on the tarmac at Seattle’s Boeing Field, it is one of four Boeing 787 Dreamliners that the Boeing Company began test-flying in December. The aerospace giant plans to deliver the first finished 787s to launch customer All Nippon Airways late this year, opening what Boeing claims will be a new chapter in aviation history with a game-changing aircraft.

The 787 has been in development for nearly a decade, its components crafted around the world by Boeing and its far-flung manufacturing contractors. ANA had hoped to start flying the new plane in 2008 in time to fly it to the Beijing Olympics, but the 787’s complicated supply chain and the technological challenges of building a new airplane have pushed back delivery to the Japanese carrier five times. Now, Boeing executives say, the 787 is nearly ready.

Boeing wouldn’t tell a visiting journalist how much money it has spent designing and manufacturing the Dreamliner, or even how many employees are working on it, for fear that I could tell competitors, especially archrival Airbus, the big European consortium, too much.

One thing Boeing executives are very happy to talk about is the rich order book for the 787. “This airplane is really resonating with airlines,’’ said James A. Haas, Boeing’s director of 787 marketing. “They are most excited about lower fuel-burn and lower operating costs.’’

According to Boeing, 57 airlines have ordered a total of 866 Dreamliners at a list price of about $150 million per aircraft. Big customers, like ANA, which ordered 50 planes in 2004, and International Lease Finance Corp., which has ordered 74, typically get hefty discounts. But revenue will still be substantial for Chicago’s Boeing, which last built a new airplane, the 777, in 1994.The company hails the 787 as “the most successful launch of a new commercial airplane in Boeing’s history.’’ Major airlines such as Continental, United, Air Canada, Lufthansa and Singapore Airlines have ordered the plane.

Boeing markets the 787 as a fuel-efficient plane with low operating costs, thanks mostly to the extensive use of composite materials — durable, flexible, lightweight, carbon-fiber reinforced plastics — which are matched with aluminum, titanium and steel traditionally used in aircraft. The Dreamliner is about 50 percent composites by weight, according to Boeing factory manager Kathy Moodie. The 777 — Boeing’s popular “triple-7’’ — is 12 percent composites.

Unlike earlier Boeing planes, which were largely built from the ground up in plants in and near Seattle, some 30 percent of the 787 is made outside the United States, and additional work is carried out at factories around the U.S. Major 787 parts are flown in on four enormous, specially modified Boeing 747s, dubbed Dreamlifters, then wheeled onto the factory floor and snapped together by Boeing workers at its cavernous factory in Everett, Wash., 30 minutes’ drive north of Seattle.

“By flying in parts, we can move much faster than moving them by rail and sea,’’ said Moodie, director of 787 final assembly operations. “It’s a just-in-time process; we don’t have inventory storage. We get the parts in a day.’’ When the factory is up to full speed, Boeing expects to do final assembly of a plane in three days.

The Dreamliner team is led by senior executives in the Boeing Commercial Airplanes unit. They are optimistic when they talk about the new plane, but Boeing has had an often-turbulent ride with the 787. This is not unusual with new-generation airplanes. Airbus has fallen behind scheduled production of its Superjumbo A380 double-decker, due in part to the extensive electrical wiring needed for the big plane, which has been used commercially since October 2007, when Singapore Airlines put the first one into service.

Boeing shook up its management team after the 787’s production schedule lagged. In December 2008, the company tapped Scott Fancher, a 33-year Boeing veteran who last worked in Boeing’s money-spinning military unit, as vice president and general manager of the Dreamliner. Looking relaxed in his office in an open-necked shirt, Fancher outlined the 787’s history and remarked matter-of-factly, “I tend to work the more complicated projects.’’

Boeing claims the relatively lightweight 787 will burn 20 percent less fuel than a conventional plane its size, making the 787 both more efficient and environmentally friendly. The twin-engine, wide-body aircraft, which comes in three different models, will have a range of up to 8,500 nautical miles, making it a prime choice for long-haul flights. It is, moreover, designed to be quiet and soothing to look at with LED interior lighting and soft curves. It will have enhanced cabin pressure, putting more humidity into typically dry airplane air. It is designed to minimize turbulence, turning big bumps into little ones.

The 787’s extra-large, oval windows are placed higher on the wall. The idea is “to reconnect passengers with the sky, to make every seat a window seat,’’ said Colleen E. Rainbolt, regional director, passenger satisfaction and revenue marketing. ‘‘In focus groups, we found that people all dream of flying. They think there’s something magical about it. This is a lot more than functional, it’s about the passenger experience.’’ The 787 is also designed to be easy to maintain, thanks in part to the composites, which don’t fatigue as quickly or corrode as easily as metal, and because it has fewer parts. Boeing promises that easy maintenance will allow airlines to put the plane in the air more often, maximizing airline revenue. Aviation industry critics have questioned whether planes that make such extensive use of composites are ready for prime time, especially through years of wear and tear or in the event of crashes. Boeing retorts that composites, which have been used in smaller amounts for years, are safe.

The Dreamliner — the moniker was picked in a public name-that-plane contest — grew out of an earlier project, conceived in 2002, to build a super-fast plane called the Sonic Cruiser. But Boeing’s marketing research showed that a big, pricey, fuel-hungry plane — flown between huge hub airports and built to funnel passengers onto connecting flights — wasn’t what many airlines were interested in buying. They wanted a smaller, lighter, more economically efficient plane that could be flown point-to-point, able to serve not only big cities but mid-sized markets — Seattle, say, to Venice, nonstop.

This sent the Boeing brain trust back to the drawing board. Boeing already made planes for point-to-point flying — among them, the 767. But the new plane envisioned by the company’s engineers would take what the 767 did to a new level. The revised plan called for a dramatically new aircraft, initially called the 7E7 (since 2005, the 787). The decision was made to ramp up use of composite materials — and to contract out much of the airplane’s hardware, instead of making it in-house, as Boeing had largely done since Bill Boeing started the company back in 1916.

“This is a large program,’’ Fancher said of the 787. “This gives us the opportunity to utilize the capacities of our partners. Diversifying the supply base is a calculated decision.’’ And, as it turns out, a calculated risk. The risk hasn’t always paid off, as contractors subcontracted some work to third parties that had not been vetted by Boeing. Some projects were delayed; others didn’t measure up to Boeing’s standards. As a result, Boeing says it tightened its control of the program. In one case, it simply bought a South Carolina 787 contractor and renamed it Boeing Charleston.

Today, four floors above the 787 production line in the Everett plant, a glass-paneled information technology office called the Dreamliner Production Integration Center monitors the status of every 787 project around the world and tracks the movement of parts in real time. The PIC is illuminated by a vividly blue, 40-foot-long “situational awareness’’ video screen and bristles with 27 work stations. Distant contractors are given hand-held videoconferencing cameras to use for talking to Boeing.

“With hindsight, we saw that we needed more control,’’ said Moodie, who frequently walks the factory floor as mechanics clamber over the partly assembled hulks of 787s. The planes-to-be advance to each of four positions where they are assembled by specialized teams who do the same jobs over and over, so they can get the processes down.

“This has a lot more repeatability’’ she said, ‘‘a lot less hardware variation.’’ Unlike the 777 assembly line in a different part of the Everett factory, there is little staccato noise from tools such as rivet guns; Dreamliners take 80 percent fewer rivets than the mainly aluminum triple-7s. Indeed, the 787 factory floor is surprisingly quiet. On the margins, workers sit at desks, beavering away on personal computers. This, too, is a break from tradition; white-collar workers usually toil far from the factory floor. Their presence is a reminder that this is a new plane made in a new way.

Boeing executives characterize the 787’s widely reported manufacturing and logistical snafus as growing pains. From Fancher on down, they maintain that awarding work to partners like Japan’s Mitsubishi Heavy Industries, which makes the 787’s wings, and France’s Latecoere, which makes its passenger doors, is a natural and inevitable way of doing business in a globalized economy.

Besides, Moodie attested, “There has never been an airplane where we have built everything. We are not in the engine business.’’ Rolls Royce and General Electric make the 787’s jet engines. “Any new airplane in the future will be a joint venture,’’ she declared.

Fancher thinks so, too. “The business models in aviation are evolving, as they are in other businesses,’’ he said. “We are looking for synergy, optimizing who does what on the airplane.’’ The making of the 787 goes on 24/7, around the world, on an ongoing basis. When close-order drills are called for, Boeing dispatches teams of engineers to meet their colleagues. “We work shoulder-to-shoulder.’’

In these last months before the first deliveries, Boeing engineers are fine-tuning the 787’s aerodynamics, and Boeing’s sales staff is busy suggesting ways customers can configure passenger cabins to burnish their brands and differentiate themselves from competitors. Depending on the model and seat arrangement, the 787 can carry from 210 to 330 passengers.

In March, the 787 passed a “flutter” resistance test — flutter being aviation-speak for shaking in an airborne aircraft. Test pilots also checked the 787’s “ground effects” — how it handles during take-off and landing. Boeing pilots will test the aircraft in extreme weather, seeing, for example, how it does in polar cold and tropical heat.

Mike Sinnett has worked on the 787 since day one. In February, he became chief engineer for the Dreamliner. Sinnett, an airplane enthusiast whose father worked for McDonnell Douglas, recalled going on test flights for the 777. He said the 787 will be similarly tested.

“We took a triple-7 to northern Sweden, Greenland and the North Pole for cold-weather testing. We flew holding patterns right over the pole.’’ It was amazing, he said, to see the plane’s instruments read ‘‘south’’ in every direction. ‘‘No one else is around. You can concentrate on one thing. You go out looking for high crosswinds in places like southeast Alaska and Iceland.’’

Sinnett acknowledged the global nature of creating a state-of-the-art aircraft. But, he added, the core of the work remains in Boeing’s U.S. factories and especially in Washington state. “Final assembly is being done here. Intellectual assembly is done here, too. The heart of the design integration is here.’’

Boeing maintains that once you’ve plunked down your $150 million for a Dreamliner, you can design and tweak it to your heart’s content — inside, anyway. “You can make it look like anything you want. You can make it look like the lobby of the Peninsula Hotel if you want to,’’ said Haas, the marketing director.

Boeing has constructed a purpose-built Customer Experience Center exclusively for 787 buyers to show off ways the interior of the aircraft can be configured — where the seats can go, how airlines might like to highlight the plane’s high, domed entryway that Boeing likens to the psychologically uplifting nave of a church. Airline representatives visit the center and stay up to five days to pick and choose. Boeing boasts that the facility is the first of its kind in the world.

Boeing is well aware that Airbus is building its own mid-sized, long-range plane. But Boeing executives believe their three-year head-start in production gives Boeing a competitive edge over Airbus and its bigger, heavier A350, which will also use cutting-edge technology. The Dreamliner, Boeing insists, is unique.

“Every 20 or 25 years, a new generation of aircraft is called for,’’ Scott Fancher observed. “This is like the transition from narrow-body to wide-body, from propeller-driven to jet engines.’’