I noticed that when I use online flight planning resources, they provide an "auto-routing" option for my flight. I also noticed that they are the same between both services so it seems like both are pulling the route from somewhere. Additionally, the auto-route appears to be different than a "preferred route" because, for example fltplan.com will say "No Preferred Routes or Stored Routes" then it gives me (a sometimes crazy) auto-route.
Are auto-routes predetermined or is it just an algorithm (i.e. nearest intersection/victor airways to destination)?
Extra Credit Question: If there is no preferred route for a given destination, is filing Direct or using the auto-route more likely to get you a "cleared as filed?"