First off it's important to know that the 100ml limit for liquids doesn’t apply to formula, or the water you need for making it, so technically you can take as much as you'd need to last the flight. Be sensible though, you can't take 'unlimited' supplies, so factor in your flight length and consider possible delays and make sure bab has enough to get through.
Official details are available here:
You do however, have to be prepared for security to want to test / make you taste it, so have it at hand, not buried deep in your bag.
My experiences of security with the baby have been good. Usually you get whisked down the family lanes and don't have to queue for ages, but just in case you're going to be faffing checking in prams / getting bottles of formula out of your bag, dealing with a sleepy baby etc, I personally would advise always giving yourself a bit of extra time it just means you're not rushing which is always a bonus should you suddenly need to factor in a change/feed.
You might usually use powder and make bottles up yourself, but don't forget you can buy ready-made formula in bottles that are actually less than 100ml, which makes the security situation so much less hassle.
If you do use powder, it could be a good idea to pack bottles with pre-measured amounts of formula powder, plus bottles of cooled, boiled water to make up the formula en route.
You can also order stuff in to pick up AFTER security. So if you think you're going to need a lot, or you just can't be faffed with taking it through security, this might be the option for you. You can call Boots in the airport and order it in. In fact you can order most of your baby essentials, so if you're short on time or space, you can do things this way. Just be sure you've ordered to the Boots in the right terminal!
I'd also advise taking the formula your baby is used to. Although strict guidelines for formula means technically all formula is the same, babies can be fickle and you don't want to find that out while you're abroad.
Don't forget to take loads of bottles onto the plane. You know what it's like when baby either decides half way through a bottle that they aren't going to finish it, or they fall asleep? Well let's face it - you aren't going to be sterilising that bottle at 30,000 feet, so make sure you have spares, spare lids and maybe a plastic bag or two to put the dirty ones in.
As with all babies, take muslins and a change or two of clothes. You don't want a baby covered in formula / puke on your lap for four hours!
Sterilising wipes are brill and really useful, as are sterilising bags and Milton tablets. If you have an older baby and don't sterilise anymore, don't forget some washing up liquid!
If once you're away you're going to be using powder to make up bottles, you might want to check your hotel / accommodation provides a kettle for boiling water, and you might want to consider packing a flask if you want to transport hot water around with you.
Don't forget the tap water in some countries still can't be drunk by babies even after being boiled, so consider bottled water (still has to be boiled first) and check the mineral content:
Look for Na on the label, which means sodium, and choose one that contains 200mg or less of Na per litre. Check the levels of sulphate (SO or SO4), too. The sulphate levels should be no higher than 250mg per litre.
Packing cubes are brilliant for a gazillion things, transporting bottles and muslins and pots of powder is just one of those things. I can't recommend them enough.
Written by Amy Clowes
Amy is Seatkickers' editor, she lives in Manchester with her daughters aged six and seven months. She loves interiors, jogging, cooking and travelling. Her favourite places include Miami, Biarritz and Cornwall.