X-Plane Switching from Auto to Stabilize

[Kevin]

In X-Plane when flying between way-points in auto mode and after about 20 minutes the autopilot automatically switches into stabilize mode.  Any ideas or suggestions on how I might correct this and if this is something to do with X-Plane and not something to be expected in a real world scenario?

[Chris Anderson]

Do you have the free or paid version of X-Plane? The free one has a timeout, as I recall.

[Kevin]

I have the paid version.  Another thing is that on the transmitter I have only two modes (manual and stabilize).  When flying in auto mode I turn off the transmitter to save battery.  When the transmitter is turned off the autopilot goes into stabilize mode automatically which is expected.  From the apm I then change modes to auto and the plane starts to fly the designated flight plan, but it is after about 20 minutes that it switches to stabilize mode.  I am pretty certain it has something to do with the mode being set to stabilize on the controller and the transmitter being off, but I can't figure it out.