Today the airline industry is large and varied. If you want to fly nonstop from New York to San Francisco, you can make a reservation on any of a number of domestic commercial airline flights. An around-the-world tour is arranged through an international commercial airline.
Much of the success of an airline stems from the careful selection of the aircraft it uses. Other things being equal, airline passengers favor the airline that gets them there first. Speed is one of the factors in attracting passengers. There is a constant race among the airlines to be the first with newer, larger, and faster planes.
The design of an airliner evolves slowly. It is usually a compromise between what several airlines want. The present realities also play an important part in the design of a commercial airliner. For example, the sudden jump in the cost of jet fuel has made a lot of the aircraft currently flying too costly. And other aircraft are too noisy to meet the new environmental rules! The airliner of the future must be quiet and it must be economical to fly.