Fuel problem in flight. (Maybe flight model problem?).

[Jollyroger]

I ran 5 flights over the past couple of days to check all the data.

Flew in an MD88 (3 Fuel Tanks) and a Boeing 737-900 (3 Fuel Tanks).

I had 2 instances of my plane just dropping out of the sky while in mid flight and on autopilot. In each instance I used the "Compare Fuel Method". All tanks were topped off, planes were trimmed and on autopilot at 36k ft. level flight.

On the first two times, I had left for a minute to get something to drink and when I came back, the plane was back on the ground and FlyNet said that I had crashed.

I ran the flights again and discovered that as soon as my wing tanks were empty, the engines cut-off, even though there was at least 3/4 of a tank of fuel left in the centerline tanks. Again, my planes dropped from the sky like rocks.

This may be a problem with the compare fuel method and the fuel burn rate, or a problem with the flight model of the planes I'm flying and the FlyNet Database.

The 737-900 is the OpenSky plane.
The MD-88 is one I got from AVSIM.

Any help from the community or the staff would be greatly appreciated.

Once more, great job on the client.