Using a base mesh and textures, the game utilises your internet connection to stream even higher quality terrain data onto your PC as you play, via the
Azure cloud. It is a novel way to boost the game's fidelity and diversity that I've yet to see in any other release.
This is indeed a fully fledged 'power of the cloud' implementation that delivers something that just wouldn't be possible to the same fidelity with a conventional download. It's a system that's also relatively efficient: over 10 hours of gameplay, I noted downloads of around seven gigabytes in total.
It's not just environment detail that's streamed in either. Flight Simulator also accurately renders the real-time world location of actual planes in your vicinity. Weather is accurately simulated based on other real world data too, down to thunder storms and cloud rendering. The aim is to represent real world flight and weather conditions 24/7 - it's ambitious, it's unique and it works. (
Source)