With the implementation of ADS-B, FAA researchers expect to see a significant drop both in aircrafts' environmental footprint and fatal accidents. This slide was taken from the agency's NextGen 101 plan (PDF) for transforming a system it says is currently "not performing adequately" and is not "scalable."
A recent New York Times story on ADS-B and the FAA's NextGen plan said the U.S. air traffic system normally handles about 50,000
flights per day, and in the first half of 2008, more than 25 percent
were either late or canceled. Flights are currently down, due the economy, but
by 2025, the FAA predicts daily air traffic will be up to 80,000
flights, the story said. "The current system is struggling badly. By 2025, it will not
have a prayer."
The estimated cost of the NextGen plan, which maintains radar as a backup navigational technology, is about $4.6 billion in the first five years and $15 to 22 billion through 2025, according to the FAA.