Philadelphia ? Federal officials showcased an experimental air traffic control system that would let pilots see other nearby planes and help prevent gridlock in the skies.

The Federal Aviation Administration hopes the satellite-based navigation system will replace the current land-based system in the coming decades.

On a flight out of a Philadelphia airstrip on Friday, the FAA demonstrated parts of the system to a group of reporters. During the U-turn flight between Philadelphia and suburban Washington, D.C., the plane used current navigational systems, but officials showed how the new technology worked.

A small, brightly colored screen provided a detailed picture of all the planes nearby, which showed up as green triangles. The system uses GPS signals to give pilots information.

The agency hopes the so-called NextGen system can eventually help reduce flight delays by allowing aircraft to fly closer together in the crowded skies and enabling pilots to weave their own courses.

The FAA is asking Congress to approve $4.6 billion over the next five years for developing the system, now being tested on flights in Alaska. Development could cost $15 billion to $20 billion.