K.S.
Hi A.,
We actually just flew to Germany for the weekend a couple of weeks ago with our then 8 month old daughter and I am getting ready to fly to Australia with her next week. A couple of suggestions: did you know most international planes have bassinets? If you haven't contacted your airline and requested one, do it now! If you did purchase a seat for your son, if he sleeps well in his car seat, bring it on the plane. If you don't have a seat for him, don't worry, the bassinet is a big help. Make sure you feed him on take off and landing (the sucking helps pop their ears, it does make a difference so wake him up if you can to feed). Once there, it will really depend on what sort of sleep he got for the plane ride, we found that my daughter actually didn't sleep her usual 11 hours so when we arrived, she was ready for bed and just went right into her usual routine even though we were 8 hours different in time.
Bring plenty of food for him (and a pump for you if you are still BF, it will make you more comfortable on the plane with the air pressure if your son doesn't want to eat much). And remember his favourite toys, it will make it more enjoyable for you all! Going through security with a stroller and car seat takes a lot of work, if you don't need to take them, leave them behind. (We took both to Germany as we needed them but I'm not taking either to Australia) If you have a baby bjorn or a wrap of some sort, I would highly recommend it.
Good luck and remember, your son will feed off your emotions so if you can keep calm and relax (easier said than done, I know!) it will make it easier on all of you.
Enjoy Ireland!