Birds do it. Bees do it. Even Orville Wright did it. Why can't today's pilots do it too?

"It" is "free flight," an alluring notion thrust into official awareness by a passionate group of pilots and researchers in the mid-1990s. Free flight, these advocates argued, would transform aviation from, well, the ground up. The idea sounded simple and intuitive, and at the same time radical: Free pilots from the rigid, circuitous routes imposed by ground-based air traffic control, and let them choose the quickest and most fuel-efficient paths around wind and weather. New satellite, computer and communications technologies would keep aircraft from crashing into one another. Planes would fly faster, cheaper and even more safely, avoiding the gridlock that currently threatens the overloaded air traffic system.

Today, five years after Congress validated this vision and the Federal Aviation Administration (FAA) set out to realize it, free flight is still sitting on the runway. Air traffic is more congested, more delay-prone and scarcely any freer. "The whole idea of free flight' has kind of fizzled," says Heinz Erzberger of NASA's Ames Research Center, the lead scientist in the development of a more limited air traffic automation scheme now coming into use. The FAA and its constituents have retreated from a comprehensive free-flight agenda (what some critics call the "Big Bang" approach) to limited demonstration projects and incremental improvements.