London is a ton of data and it’s not just the 100+ mbps sustained you need to pull it in fast enough, the sim also needs to process all that data in time. If you fly too fast it quickly falls behind.
On my system I get beautiful scenes… flying 100 knots at 25% sim rate (thus 25 knots effectively). Then everything keeps up and it looks like this:
(Terrain detail 200, 1080p 200% renderscale, 4K render resolution downsampled)
It ‘runs’ at 5 to 10 fps, flying along at 25 knots. It’s the most beautiful screen saver yet though!
(straight line London City Airport to Heathrow consumes 4.38 GiB of data at terrain detail 200)