SLOP's
Sorry, I'm a bit of a lurker - but very interested in ATC and safety matters.
I have been looking at the NAT procedures and offsets and specifically SLOP's.
From what I can work out SLOP's are upto the pilot to choose, i.e. Centre, R1 or R2 - but I think I read elsewhere there is an option for the pilots once in the air, to communicate amongst themselves - does this happen in reality?