How about North Atlantic Tracks - no radar coverage and the first to introduce RVSM!!!!!!!
1. Operated in an environment of excellent VHF transitions to very good HF comms in a highly monitored manner
2. Operated in a generally more benign wx environment (at least as far as fewer wx deviations required)
3. Operated in a fixed track environment with quite few aircraft crossing tracks
4. Operated generally by modern aircraft, well maintained by international scheduled airlines from well regulated countries
5. Operated usually with 98% of traffic going in same direction on a given track
Now lets talk about Africa again ...... need I say more?