Changing Air or aircraft cfg files (except for new flightsim entries for liveries) with our ADV models will absolutely make them unflyable, as the flight models are external, and the airfile specially tuned to stop the sim from fighting back. That reminds me of another possible issue. If the texture pack was added, I hope the aircraft cfg was not copied over, but rather just the flightsim entries.

One other item I can also think of for P3D users: Make sure your control input source is set to DirectInput, not Raw.