Normal commercial air traffic control doesn’t go beyond 60,000 ft in altitude. That makes sense since civil flying activities have been limited to lower altitudes. In fact, modern commercial airliners are not designed to fly above about 45,000 feet. This is a compromise based on what works commercially as much as what’s works best. Aircraft instruments are calibrated making standard assumption about the atmosphere.
For some of its flight, Concorde cruised at a height of 60,000 feet. More like a military jet, with its speed it had the capability to make use of higher altitudes.
It’s even possible to fly above 50,000 feet without an engine. The world record glider flight by AIRBUS shows it’s possible.
The Earth’s atmosphere is not uniform. It changes its characteristics with altitude. The atmosphere can be divided into five layers, as the temperature and density change. They are named: Troposphere, Stratosphere Mesosphere, Ionosphere and Exosphere.
The Troposphere is a layer that goes from 8 kms (26,247 ft) on the poles to about 18 kms (59,055 ft) on the equator. This is the layer where weather is experienced.
On average, the Stratosphere goes up to about 40 kms (131,234 ft). The winds blows fast but they tend to be more consistent as they wrap around the globe. The lower portion of the Stratosphere is virtually isothermal (layer of constant temperature).
A medieval English philosopher and Franciscan friar, Roger Bacon figured out that the air might support a ship in the same way that water supports ships. In the 13th Century that was a nice academic conclusion but little more.
With all the current controversy surrounding high altitude balloons, that the road to flight started with balloons, could be said to be a bit ironic. It’s long been known about that balloons fly well at high altitudes but it’s a new frontier as far as commercial activity is concerned. For science, weather balloons may go up to 40 km to measure the high level winds.
Some experimental work has been done on trying to commercially use the airspace above normally civil flying. The Google Loon trials are an example of an attempt to float a telecommunications platform high in the sky. These balloon trials were abandoned as difficulties proved greater than anticipated.
It’s not so easy to keep a high altitue balloon on-station.
Now, considering the news in North America, maybe high-altitude operations ought to be a matter of regulatory concern. This is not a subject that any one country can address alone.
There is some legal, regulatory and technical work underway in Europe but it needs to make progress. This is a subject for international collaboration.