Extreme FPS Drops - NVIDIA 4090

Hi everyone,
Unfortunately, I have extreme FPS drops again and again. It usually occurs after more than an hour of flying. Sometimes I go from 60 FPS down to under 10 FPS (it can happen anytime within the flight). My hardware should easily withstand the requirements of the FS… I don’t know what to do next. If I end the flight and restart from the menu, I’m back to my 60 FPS. No idea what leads to this problem. Thanks in advance!
My PC Specs:
CPU:AMD Ryzen 5900X
GPU: NVIDIA Geforce 4090
The FS runs on a NVME SSD.
My resolution is 5120x1440