A caveat to Bruce’s excellent suggestion – to set your “cold start” default flight, do it from either the Cessna default conditions flight *as it opens from FS9*, not from a previously saved flight, etc. You want as “pure” a set of conditions in FS9. If you’ve made a long flight through weather, icy conditions, etc., some of the aircraft post flight conditions may be saved, and even if your next flight starts in a bright and sunny environment, the conditions are “remembered”. This is why some developers advise to first switch to a default flight before loading their models.

So, to set a new default “cold start” flight, first load up the Seattle Cessna 172 default flight, shut everything down, … adnn follow Bruce’s suggestions above..