Set up a route ahead of aircraft arrival, but since arrival may be far enough out, one would lose the route because it would not be flown within the threshold that AWS allows. Solution is to set it up without purchasing the slots, and assign the routes to the incoming aircraft.
However, after one's done that, and finds an error in their setup: - often, in the process of saving the routes one after the other, or perhaps when scheduling maintenance when all have been saved (i.e. not enough room), one cannot go back and just shift the un-purchased routes. The only way possible to access them again to change them is through the edit route window. This means that one MUST purchase them as part of saving them that second time editing.
The result is that one must discard the route and start over with all routes that need to be tweaked.
If the mistake is on a 7-day schedule, this becomes a real headache.
Related report here:http://www.airwaysim.com/forum/index.php/topic,50339.new.html#new