For routes I have one sheet for each hub with all possible routes (as copied from GateSearch). Then I take note of the aircraft ID on each route. Since I have another sheet with my fleet (and info on range, speed and turn time of each plane), a couple of formulas are enough to know exactly how much time each plane flies and, more importantly, how far it can still go.
By using filters I can locate very rapidly suitable routes.
One simple trick is to use colour coding (with conditional formatting) to have adequate destinations stand out from the croud.
For deliveries and such I have a very simple planner (yet another spreadsheet) where, for each (game) day, I have the indication of the real time, projected cash and, of course, where I make note of planned deliveries.
