I wanted to fly GVA-ZRH on the 737-400. I made my flight plan using the Flight Planner. After I took off, I set the altitude to 20,000ft., turned on the autopilot switched on Altitude Hold and let go of the stick, but nothing happens! The plane all of a sudden drops, and I have to take control of it again.
I flew many flights in FS2000, and have not had any problems with the altitude hold.