Hello,
My sistem specs are the following:
CPU: Intel i7-11700K
GPU: Nvidia RTX 3070TI
RAM: 32GB
Windows 10
As I said, I had this problem at the release, but it was gone long time ago. And now, after the latest update, I had it during a flight from Helsinki to Gran Canaria. When I hit x4 time acceleration I am around 15 fps, but in the middle of the ocean and at 40.000 feet is unnoticeable. Furthermore, other aircrafts with time acceleration do not behave like this (such as PMDG 777 or A380 FBW). Only yours.