There are two types of scattering in the atmosphere :
- Rayleigh Scattering : This scattering comes from small particles i.e. air molecules which diffuse light mainly in the blue (actually mainly in ultraviolet but our eyes can’t see it. If we did, the sky would be a hazy mess because there is so much diffusion in UV)
Figure 1 : Photo from flight AF166 from Bangkok to Paris on July 20th 2015, taken over Georgia, showcasing mainly Rayleigh Scattering
- Mie Scattering : This scattering comes from larger particules i.e aerosols which tend to give a whiter diffusion. That is why when the sky has a lot of humidity, pollution, sand etc it looks more white or brown. Also, with greater particules, the diffusion is greatly increased in the direction of the incoming rays. That is why at dusk, fog looks really bright when looking at it towards the sun, and looks dimmer when you look at it when the sun is behind.
Figure 2 : Photo from flight AF166 from Bangkok to Paris on July 20th 2015, taken over Pakistan, showcasing mainly Mie Scattering coming from sand particles and humidity
Those phenomenon are already well rendered in MSFS, though they have said they were going to overhaul the scattering simulation.
The big issue is that in live weather, there is absolutely no aerosol data injection, so the sky always looks like a clear, clean, dry, cold sky, in other terms very blue. When you are flying above areas with a lot of humidity, sand particles or pollution (which tend to make the sky white in real life), because MSFS doesn’t render aerosols, the sky looks much bluer than it should.