How would the TLS be affected if the Big Sky theory were relied upon
for aircraft separation as John T. suggested?

I'm not very familiar with this subject, but you can read "Safety
Considerations for Operation of Small Unmanned Aerial Vehicles in
Civil Airspace" produced by the MIT International Center for Air
Transportation:

http://icat-server.mit.edu/Library/f....cgi?idDoc=205

They studied both midair collisions and exposure to people on the ground. The
relevant conclusions for midairs:

Significant Amount of Airspace with Exposure Risk
Below the Target Level of Safety
- Areas around major airports are above the TLS

Opportunities may exist to allow a class of small
UAV’s to operate with limited restrictions
- Limiting operation in airspace near airports
may achieve TLS

Mitigation Strategies Are Available to Further Reduce the Risk
-Vehicles can be designed with capabilities to limit
likelihood of midair collisions

Barry