Flight is a little more than a century old, the jet age perhaps half that. Now its baroque phase begins with the first flight (at last) of the Boeing 787. While technically daring in many ways — half the plane consists of lightweight carbon composites — the Dreamliner refines yet again the “tube with wings” design, nave and transept-crossing of a carbon fiber cathedral. It is not the shape of the future of flight.

The Boeing 787 cost a monumental $20 billion to develop. By force of improved methods and materials, engineers wrung a further 20 percent fuel savings from this latest-generation aircraft. But the 787 dangles from the same technology arc as its predecessors, dating back to the 707 that first flew 50 years ago. That arc is now flat.

Start with engine efficiency, where the sharpest gains came early, in the flower power 1960s. Today engine efficiency ticks up a scant 0.2 percent per year. Engine temperatures have soared to near 3,000 degrees but ever more esoteric materials now push the melting point up by less and less. Computing power has scoured the last unnecessary molecules from engine designs, leaving engineering perfection — but not much room for improvement. Although amazing, engines aren’t magic. They’ve gotten bigger, so much so that the Dreamliner’s engines are nearly as big around as a 737. But they also weigh more than earlier power plants despite the use of light-weight materials.

Composites provide roughly twice the strength of aluminum at just over half the weight. By converting the biggest, heaviest parts (the tube and wing), the 787 reaps most of the carbon fiber harvest. Even generation-after-next materials like carbon nanotubes won’t produce the big yield of today’s composites.

For all the hype, weight reductions are the toughest way to eke out fuel efficiencies. Shape matters more. Passenger jets have been continually resculpted to be less brusque in forcing their way through the air at 500 miles an hour. But the changes have been slight. Half a century’s refinement has enhanced aerodynamics a slender 15 percent, and recent efforts look increasingly desperate. An example of a tiny gain: All 787 engines will be gray, because when colors meet they create “paint edges” that catch slightly at the air.

Helped by 800,000 hours of Cray supercomputer time, the 787 might be marginally more aerodynamic than its predecessors. But its cruising speed hardly differs from the 767 which it replaces.

In 1986 when the 767 was brightly new, President Reagan promised a hypersonic, ballistic passenger jet able to screech at mach 25 from Dulles to Narita in two hours. Will we see smaller government first?

The 787 is not the avant garde of the aviation future. Look again at its gray engines. Free of brush marks and carefully sculpted, the engines pass through the air like a diver leaving no splash. If more of the aircraft attained this rarified state of “laminar flow,” fuel consumption might fall to new ascetic lows. Futuristic memory alloys, which actually morph to the perfect shape around the engine in response to temperature changes, were tested on the 787 — but left off.

That’s the state of commercial aviation in a nutshell — or a nacelle: Partly embrace a new technology but exclude more radical ones. The future of smart alloys is on hold, for instance, for the simple reason that welding melts them.

"Transporting" lay people is a shared purpose of cathedral architecture and aeronautical engineering. The 787 doesn’t have stained glass but does have larger, impressively futuristic windows which change in tint at the touch of a button. But they look out from a traditional tubular fuselage. A more iconoclastic design, melding transept and nave, blurring the body/wing distinction, would move closer to the ideal of a craft that is all wing.

For inspiration, passenger jets have looked less to churches and more to the military. The original 707 looked to the B-47 bomber, its cousin and ancestor. Perhaps a completely new Boeing “808” might derive from the B-2 stealth bomber in a flattening of swords to plowshares, fuselage into wing. Boeing and NASA are working jointly on such a plane. Reagan too had an experimental aircraft in hand when he misread the shape of things to come. Why is the plane of the future always delayed?

It's not that we don't have ideas about these new planes, since most “futuristic” ideas in aviation are not really new. The flying wing concept is nearly as old as powered flight. But cost and safety buttress conservatism, holding back change. Large planes are also immensely complicated, with development cycles of more than a decade. Boeing’s “clock speed” is almost ten times slower than the microprocessor industry, and slackening as the gap between generations of aircraft widens.

Two trends might quicken aviation’s pulse. Unmanned aerial vehicles (UAVs), progeny of the war on terror, are small, cheap, and have short development cycles. These drones, like fruit flies in experimental biology, provide fundamental insight into larger organisms. With UAVs, morphing wings and other outré ideas can be tested quickly and inexpensively.

Business jets, currently under a cloud of moral opprobrium, might be another way to break through the technical barriers confronting supersonic flight as the economic crisis clears. Speed costs but the money is out there. Ever-resourceful engineers are now “shaping” sonic booms to mute the effects on earth-bound pedestrians as the elect pass overhead. The new promise is nine and a half hours, New York to Narita.

Cathedrals invoke and satisfy deep celestial yearnings, with soaring walls and spaces built over lifetimes. The 787’s thin carbon fiber skin immures the genius and vitality of its many makers. While they have lifted the passenger jet to its highest state of refinement, the Dreamliner provides no passage to the future of our imagination. Arranged on long aisles, congregants and passengers of this world still await rapture.