GEN-X is the FAA scheme to modernize the entire US air traffic control system. Today's system works on ground radar stations, straight out of World War II. Controller eyeball the radar screens and radio flight orders to airliners to keep them from colliding. The radar beams are fairly tight, 3 degrees, but that means an uncertainty of plus or minus 2.5 miles when the plane is 100 miles from the radar station. So controllers maintain a ten mile spacing between planes.
GEN-X requires all aircraft to carry a GPS and a special transmitter to send the aircraft's GPS position to the ground station. GPS is accurate to 100 feet and so the planes can be packed up tighter in the sky.
The GEN-X equipment costs $500,000 per airliner. Right now the airlines are supposed to pay for this, although FAA will make loans to airlines to fund GEN-X installation. And, the airline gets no return on investment. With or without the $500,000 GEN-X equipment, the plane gets from here to there at the same speed. All GEN-X does for the airline is cost money. It doesn't offer any benefits.
The greater accuracy of GEN-X doesn't matter. Packing airplanes more tightly together in the sky won't help move more traffic. There is plenty of sky to hold all the airplanes. The bottleneck is airport runways. An airport can only handle one flight a minute, and all the major airports have been running at capacity for twenty years or more. I picnicked on Castle Island, just off Logan Airport, and watched a never ending stream of airliners, packed up head to tail, coming in for a landing. That was 20 years ago on a nice sunny day. It gets worse when the weather gets bad.
Any how, FAA is pushing hard for GEN-X, for mysterious reasons. Our tax money at work.