RTX 3070 - FPS dropping from 45 to 25 and no help other than restart MSFS

[Ikarus 👾]

I read quite some things about my RTX having not enough VRAM.
I totally accept that this is not the perfect hardware.
However, I am not really able to help the situation.
Some flights are OK, then I load into a mission and suddenly my FPS are down to 18 and never recover.
Once I restart MSFS, I am back to normal.
Is there any chance to recover while in game?

[ждун]

this really sounds like vram overflow.
It can happen with any GPU no matter how much VRAM you have, because of memory leaks.
When you have a memory leak it will pile up data in vram until overflow. Then the GPU will start using regular RAM which is much slower and that is causing the performance break down. In worst case RAM will also overflow resulting in CTD.

You can confirm this situation by monitoring your vram usage. I am using free tool called "GPU temp" it is for monitoring GPU temperatures, but it also tracks VRAM usage. If it starts tanking you can check whether your vram usage has approached close to 100%. If this is the case your GPU is likely already in overflow state.

If you can confirm this is the case, next is to figure out if that is a memory leak or just too high graphic settings. In the latter case you can resolve the issube by simply reducing texture quality or terrain LOD. These are the options with the heaviest impact on VRAM. If it is a memory leak all you can do is wait for a fix and perhaps trying to figure out what exactly is causing the leak and avoid this situation. For example some airports in north america are having memory leaks. Some planes probably too. Flying in different areas using different planes may help temporarily until there is a fix.