I want to write a parser for ICAO format flight plans, like the one shown below.
-N0471F310 LEKPO UL617 SKP UB1 ABLON
-PBN/C1B2S1 DOF/160805 REG/SXDVD)
The thing is that everything I come across is related to flight plan filling and not about this format, what to expect, what not to expect, field meanings, possible values etc.
I am looking for something like that but formal, preferably from some ICAO document