Pinatubo wrote on Sep 6^th, 2014 at 4:54am:

I'm looking for a FSX flight planner (payware) that allows me to save either as .PLN or as .RT. Which is the best one to buy? :-/

Flight Sim Commander 9.5 Saves as .PLN, while Professional Flight Planner X saves in both .PLN and .RT.
In all honesty, FSC9.5 is better as the PFPX .RT files are NOT perfect, but PFPX has a neat feature for flight planning that allows me to find the next jet airway I need for my flight the plan!
I feel that the PFPX devs only did a half hearted job on the .RT save format. :(