Hi
As the previous posters have already written, “Sim=Cessna 152 01 Livery” is the original line.
If you want to use the C172 Skyhawk, you should not delete the “Sim=”.
It is best to use my freeware tool “MissionChanger”, with which you can easily select the aircraft and other options. MissionChanger is available at Downloads – BushTripInjector/MissionChanger