i just jumpseated recently on 2 ryanair flights to and from brussels. I just asked the fa at the door when i got in to the ac. they asked for me and they wanted some id (passport and some form of proof that you are training like ppl or logbook etc.) and no probs whatsoever,. With ryanair, get in to the aircraft first, if flying with another airline ask the dispatcher at the gate, and they'll sort it out for you. I've never ever had problems.