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2. Efficiency and Aviation Capacity
For the last 10 years, the US air transportation system has been experiencing delays, decreasing efficiency and increasing costs. The situation only worsens during inclement weather. Over the next 20 years, the demand for air travel is expected to triple, making these problems even more severe. To prevent these problems in the future, the FAA and NASA are focusing on modernizing the National Airspace System and increasing the system's throughput.

There is an old saying, "You can push only so much water through a pipe." To follow this analogy, think of each pipe as a runway. There are only so many runways (pipes) at each airport. Many of these airports have no room for expansion. Presently, for all major US airports only 15 additional runways are being built or are in the planning stage. This means that some new or longer runways will not be available for several years. If a pipe has only a quarter-inch diameter, then one cannot push through this pipe the same amount of water in the same amount of time as a pipe with a half-inch diameter. To maintain safety, aircraft can fly only so close to each other. So if a runway has a capacity of landing 40 airplanes per hour, it cannot land 60 airplanes per hour without shortening the distance between airplanes or increasing their airspeed. Such a change would compromise safety.

Within our current system there are too many aircraft flying to and from the same runways as well as flying in the same airspace. The present "hub and spoke" system used by the major airlines creates "push" times when many airline flights arrive and depart within the same time frame. Instead, the departure time frame should be extended to spread them out more evenly. These "pushes" overload the system. This causes many aircraft to wait at the gate for permission to push back. It also causes a long line of taxiing aircraft waiting for takeoff.

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