Boeing claims the so-called Dreamliner will be 20 percent more fuel efficient than comparable jets. And it promises a better travel experience, with more space, better lighting and carefully calibrated air pressure that should lead to fewer flier headaches.
United will fly its new plane from Seattle to Houston on Friday to begin getting it ready for passenger flights.
In the U.S., Japan Airlines flies 787s from Boston to Tokyo, and plans to add San Diego-Tokyo on December 2.
Japan's All Nippon Airways was the first airline to get a 787 a year ago, and starts flights Monday between Seattle and Tokyo's Narita airport. Flights between Narita and San Jose, Calif. begin in January.
United Airlines expects to get five 787s this year. Passengers will first see the 787 on flights between United's U.S. hubs. Then, on Jan. 3, United begins flights from Los Angeles to Tokyo. On March 31, it starts new flights from Denver to Tokyo Narita.
Among U.S. airlines, United Continental Holdings Inc. is going to have the 787 to itself for several years. Delta Air Lines has pushed its deliveries back to 2020, spokesman Anthony Black said. Around the industry, there's widespread skepticism about whether it will ever take the planes.
American Airlines has a commitment but not a signed, firm order for 42 of the planes, set to begin arriving in the second half of 2014.
Chilean airline LAN plans to fly 787s from Los Angeles to Lima, Peru, but doesn't have a firm date yet.
Travelers will notice the 787's bigger windows let in more light, and its ceiling is 15 inches higher than in United's 767s. The air is less dry than on other planes, and the cabin is pressurized to a lower altitude. That will make the air inside feel closer to the air on the ground.
Ray Neidl, an airline analyst for Maxim Group, said he thinks this will be the first plane since the 40-year-old 747 that passengers will go out of their way to book.
"People are going to feel a lot more comfortable at the end of a long trip than they would feel on a normal airplane," giving them a reason to seek it out, he said.
United's 787 seats 219 passengers, including 70 in what it calls "Economy Plus." That's a sort of high-end coach seat that has three more inches of legroom, and other perks.
That's a significant number of Economy Plus seats, said Tim Winship who runs frequentflier.com. But considering the long flights the 787 will be making, United appears to be betting that passengers will pay up (or use frequent flier miles) to get those seats.
For most passengers, 787 or 777 are just numbers. All that really matters is their personal space on board. And the best measure of that space is the seat pitch, or the distance between seats.
By the standard, United's 787 lands in the middle of the pack. United's pitch will be 32 inches in coach, which is roughly comparable to planes that travelers might encounter on other airlines. United and American's 777s have 31 inches of pitch, according to seatguru.com, although American's 767s have 33 to 34 inches. Delta's 767s have 31 to 32 inches, according to the website.
The 32 inches on United's 787 is "pretty much the standard for entry-level coach seating," Winship said. "It's certainly not enough to surprise or delight long-haul flyers."