Mission Planner Flight PLAN — Mission Planner documentation
RouteFinder (free access area)
Online Flight Planner - ONLY FOR FLIGHT SIMULATION
Delta Virtual Airlines Water Cooler - FSX Flight Planner, The Best !!!
ForeFlight - File IFR and VFR Flight Plans
Interactive Google Maps based Great Circle Route mapper shows actual/ideal shipping and airline routes against a mercator projection. Southern California to Southern England example[1395x694]. Link inside. : r/MapPorn
ForeFlight - ForeFlight Dispatch
Atlantic ferry flight routes
A Flight Plan In 10 Steps
AirTreks TripPlanner: Plan Your Multi Stop Trip Today