Sorry to bump up this old problem, but I've been searching everywhere on the web and forums to fix this problem.
When starting a flight in P3D loading autogen (70-80%) takes over 24 minutes on my (new and quite fast) computer.
I typically run :
P3D v4.5 (latest version)
Some Orbx sceneries
My system is a Windows 10 (latest version and drivers)
Intel i7 - 10700K @ 3.8GHz
NVidia GeForce RTX 2080 Ti