Shortly after reaching cruise, the plane turns from side to side to a point where the bank angle warning sounds. Then in a few minutes the plane turns to an angle where it loses altitude rapidly and the levels out after loosing about 4K to 5K feet, something similar to nosedive spiral. The dive is totally caused by the autopilot there is no input on the controls by me.

Hello, Sorry I cant help you personally, but if you go to the last post in the 737 Topic entitled "Strange issue during flights" you will see it has the same issue as you have, with answers. hope this helps. richard welsh

I'm guessing that this is in some way related to your weather engine settings. You need to disable turbulence.

I'm guessing that this is in some way related to your weather engine settings. You need to disable turbulence.

 

I had the same problem too, its something to do with wind turbulence. If you have Activesky, enable Direct Weather Control and turn off wind turbulence, and if you use anything else either turn off turbulance in the FS weather settings or set FSUIPC to smooth wind changes.

Alright, I'll disable turbulence settings and report back.