http://www.npr.org/blogs/money/2014/05/30/317074394/drone-wars-who-owns-the-air

It's a question that goes back to the middle ages, to a Latin
phrase that translates to "he owns the soil owns up to the heavens." In England,
this phrase was the law of the land for centuries, and it worked well when
disputes involved simple things like overhanging tree branches and lopsided
buildings.

But once hot air balloons and airplanes came into the picture, things got a lot
more complicated. In 1926, Congress created what we now call the FAA, and
declared that the air above 500 feet is the public domain. But what about the
air below that?

Thomas Causby was a chicken farmer in North Carolina who lived near a tiny
airport. During World War II, the army took over the airport, and suddenly big
military planes were flying over Causby's chicken coops all the time. The planes
scared Causby's chickens. They flew into the walls of the coop and they died.

Causby sued the government, and the case went all the way to the Supreme Court.
In the end, the Court sided with Causby, ruling that landowners own the sky
above their homes up to at least 83 feet.

But the decision still left a gap. If the air above 500 feet is public property,
and the air below 83 feet is private property, what about the space in between?

This is the territory that entrepreneurs dreaming of drones have their eyes on.