[ertemplin]

If the airplane isn't in the clouds and is below 18,000 feet MSL the pilots are still responsible for seeing and avoiding other traffic. There are a lot of places in the USA that don't have ATC radar coverage, so traffic separation is based almost entirely on see-and-avoid and cloud distance laws for VFR pilots.

The ATC problem is probably the easiest one to solve, and there are already some solutions in use like D-ATIS and automated pre-departure clearance (PDC).

[sokoloff]

If that airplane isn't in clouds and is at/above FL180, pilots are still required to maintain vigilance to see-and-avoid other traffic. It's true that positive separation is also provided by IFR rules in class A airspace, but any time you're in visual conditions, you're expected to see-and-avoid.

FAR 91.113.b: https://www.law.cornell.edu/cfr/text/14/91.113