Don't worry! It's not as daunting as it sounds haha. But i've never been on long haul flights tho.. just remember to bring his swaddle cloth (to line bassinet) and the things your bb likes. Some toys and i suggest to bring the whole can of formula! You might not know how much you need so is just in case.. if your bb use paci, do bring it! Let bb suck (or let bb drink milk or latch on you) during take off and landing. Bring books or rattles anything with sound that can distract him (but not so loud one lah). Bring extra blanket, 2 or 3 pairs of clothes, some small hanky to wipe him and 2 packs of wet tissue (just in case!) It's gonna be a very bulky flight so prepare 1 normal diaper bag that's easy for you to navigate and 1 small hand carry to keep extras. That might not be all so pls look into other mummy's insights. Good luck! Oh! V impt is bring along bb carrier!
No need to premix the formula. The airline can help you make the milk when you need it.