In your carryon
Take a change of top for you (and emergency leggings as well) in case of vomit getting all over you.
Take at least 3 changes of outfit for ds..babygrows with the least complicated fasteners for the win
I would package up a mini changing kit to take to the loo as they are so small my whole carryon bag didnt really fit in there..so a pouch with a nappy, wipes and and cream..then would refill it once I got back to my seat to be ready for the next excursion
Be really strategic with your carryon, I am guessing you will get 2 pieces, one to go above and one smaller one for under the seat in front. If you can find a bag that opens up fully for your smaller option it makes it easier to find things in it, rummaging through a bag while sat in economy with an infant on your knee is v difficult
Pack everything into packing cubes in your carryon..so toys in a blue cube, nappies and wipes in a red cube, chocolate and snacks for you in a yellow cube..then its easier to just yank out the color you know has what you want in it.
Take some sealable bags with you for the smelly baby clothes with the poonami or vomit on them, so you can seal then and stuff them in the bottom of your bag, take a few other small bags to use for rubbish bits and pieces
Take a reliable water bottle that wont errupt all over you when the pressure changes, you can fill it after security
Take snacks for you..eating the meal might be tricky
Try and avoid squeaky toys, but crinkly books and things that click and squish are excellent. If you can find a way of tethering them to something like the seat belt, then it will help retrieval when they get dropped or thrown etc
You can walk up and down the aisles and chat to the air crew, take ds to look out of the window in the lobby area, you dont have to stay in your seat unless it is bumpy
Make sure you have a specific pocket for your passport, money and boarding pass that zips and only ever put them in there..mislaying something important is likely and horrific, so be very vigilant about that
You will want to feed at take off and landing, but if ds is a ‘quick feeder and then done’, dont start until you are speeding down the runway at take off and he is starting to fuss on the descent. It can take a long time to get the plane up and down, and you dont want to waste the feeding time on a moment when he isnt in need of swallowing
security is a pain in the bum, there is no way around it. Make sure you know the rules for the airports your are going through, arrange your liquids etc for easy access, and then just take your time and dont get flustered
Have fun, it will probably be a lovely trip