So the balloons just float on the air channels 20km up and presumably circulate around world? I can imagine problems coming up with some countries objecting to these being over their airspace.
Most countries seem to claim somewhere between 70Km and 100Km as their airspace.
If someone has more details on this, it's very welcome.
Besides, a lot has changed in the use of airspace and space in the last 8 years.
Yet, I don't know of any authoritative source for the actual current claims of most countries.