Hi Ruth, BIG congrats and have fun in Lisbon. We recently went to Majorca with our 4.5 month old, checked the buggy in with our other bags (just had to take it to the oversized section) and then used the sling whilst at the airport, for me it was the easiest way to do things as when he fell asleep I was able to just leave him on me and get hubby to put the seat belt on us both rather than waking him and having a grumpy baby on the flight. However we're pretty light packers so I only had the baby bag & hubby his camera bag so very little else bar baby to carry. Depending on who you're flying take seats with a gap (so if a three configuration take the window & outside ones) and then let everyone coming towards you see you have a baby, generally they then avoid you! :-) So unless the flight is full or you're flying with someone nicer than Ryan Air or Easyspace you get that extra seat for the three of you. If you can pre book seats then I'd still go for booking a 3 as most people will still avoid a single seat and will generally swap if they do end up sitting between you & hubby - all sounds a bit complicated in how I've explained things but hopefully you get the general gist of it..! Have fun.