How B777 is called 21st century airliner?

Answer 1

Because of the materials used in its construction, the methods of design and manufacture, and the design.
It is made largely of composites that are stronger and lighter than aluminum.
It was designed using computer software that allowed fitting parts together and enforcing that fit so that errors were sharply reduced. It is manufactured by many different companies using that software data to avoid errors and make larger parts so assembly is easier.
The design is for a large plane with fewer engines for efficiency in carrying more passengers. It is closely matched to the kind of plane airlines want for the kinds of routes that passengers want.

Answer 2

In addition to the other two answers; The Boeing 777 was designed to carry passengers in the 21st century (obvious answer). Also, it is the first large airliner which is perfectly symmetrical (round). Previously, designing a plane fuselage like this was a "no-no". However, as the person before answered, it is now possible with very precise machine work (called NC-Machining which stands for "Numerically-Controlled Machining"), new very light and very strong composite materials, and computer-aided design (known as CAD). All of this collectively were "firsts" for this aircraft.

Trivia: Did you know that certain customers who purchase the 777, use the Rolls Royce engines. The diameter of these monsters (just the intake) are as large as the entire diameter of a 757 !

Answer 3

It's the only airliner that has been designed completely by computer. all parts and components.