Boeing announced this week that it had finally completed test flights of its Rolls-Royce-powered 787 Dreamliner. The "first-of-its-kind jetliner" is partly made of a lightweight composite plastic, giving it greater fuel efficiency and the ability to travel greater distances than standard midsize planes. It's been delayed for three years, but delivery of the planes — Boeing's fastest-selling commercial jet ever — should finally begin later this year. Here, a brief guide by the numbers:

Low estimate of Dreamliners that have been ordered so far by more than 50 airlines around the world, making the plane the fastest-selling commercial airliner in Boeing's history

$185.2 million
List price of the Dreamliner

Number of 787s Boeing is now building each month

Number it expects to be building each month in 2013, when it ramps up production

More than 3
Number of years late the Dreamliner is. Japan's All Nippon Airways is set to take delivery of the first planes in September

65 percent
Increased size of the Dreamliner's windows, compared to the industry norm. The "gigundo windows" don't have shades but can be dimmed or brightened, from completely dark to clear, at the touch of a button. They are are made of two layers of glass separated by a gel that has a chemical reaction and darkens when electricity is applied to it.

20 percent
Improvement in fuel efficiency the new plane will have, compared with other planes its size, according to Boeing. The Dreamliner's fuel needs have been reduced with advanced engines and the use of lightweight composite materials in its wing and fuselage. Since it burns less fuel, it pollutes 20 percent less, too.

8,200 nautical miles
The longest distance the plane can fly before refueling, making it the first midsize plane with such range. According to officials, up to now only gas-guzzling jumbo jets like the 747 and 777 could go that far.

Number of cities the Dreamliner will connect that are currently served only by larger planes, according to Boeing estimates

Number of passengers the Dreamliner can fit

Number of holes drilled into a 747 during assembly

Fewer than 10,000
Number drilled into a 787, thanks to a its sleek design

30 percent
Maintenance savings airlines could see thanks to that sleeker designer, according to Boeing

Number of hours of flight testing the 787 had completed as of Aug. 15, 2011

Sources: Airline Reporter, Baltimore Sun, Business Insider, Reuters