Instead of sticking to fixed “air routes” for the convenience of busy controllers on the ground, planes would fly direct to destinations, choosing their altitude, steering around weather. Planes would fly closer together safely. Landing would be a smooth and continuous descent from altitude rather than a laborious stairstep with a controller barking instructions at each stage.

The system, known as “free flight,” would be a huge saver of fuel and passenger productivity. By the late 1990s, it was also supposed to save the traffic system from absolute gridlock. Then came 9/11, which reduced demand on the system. Less noticed, so did the consolidation of America’s network carriers. One corollary to crammed planes and more profitable carriers is fewer flights: In 2005, the U.S. hosted 11.3 million commercial takeoffs. Last year, it was 9.6 million.

This remarkable shrinkage has enabled the natural tendency of the FAA and Congress to procrastinate, waste billions, and become hopelessly bogged down in log rolling so that free flight, and thus drone integration in the traffic system, is further off today (at least a decade) than it was in 2005.