Funnily enough DFC I DO know what a FPL is and have filed probably more than most in my 15 years in ATC. I have yet to see RIF in item 18. You have still not told me what it stands for. I cannot find any reference to RIF anywhere. My other half who used to work as a International Flight Planner has also never heard of this.
As far as I am aware you are not allowed to get airbourne with the intention of going anywhere other than your filed destination. If then you find you have incorrectly calculated your fuel you divert.
I stand corrected, I have found a reference to RIF. Still never seen it or find anyone that has on a flight plan.
RIF/ changes of routing to the changed destination aerodrome and/or changed destination aerodrome
http://www.ivao.org/training/tutoria...lightplans.htm