Just to echo all the above sentiments - even the Calpol! : Travelled almost yearly by myself with , first kid at aged 6 months, and then the 2 kids starting aged 4 and 1 - now 10 and 7 - on journeys that took over 24 hours start to finish. Trains, planes and automobiles. I put pencils , pens, coloring stuff and new cheap lego stuff into zip lock bags, so everything was individually packed and easy to find in either their or my handluggage. Same for small snacks etc. I swear by coloring books , maze books, join the dots etc., and kids cards, like Old Maid, that they have in the Educational toy shop. Play at home a bit if he/she isn't used to it. And I'd second the Argos catalogue idea. My kids loved it. If your kid is at the gameboy stage ( at 5 ? not sure ) then that's your most treasured possession and should be cradled lovingly and not let out of sight while you sip your G&T in the airport lounge ! If the plane has the individual screen then , again, you'll be freed from being the entertainment manager for the flight. And do the walking the aisle thing for a while. I always found the passangers to be friendly enough to passing toddlers.
Good luck.
