Yes - In our experience you can take the formula both on the plane (whilst flying) and in your hold luggage.
The infant formula we have taken abroad has been in both premix and powder form and both made it through security at Gatwick, Heathrow and other international airport security checks. Only on one occasion was I asked to taste my daughters water bottle.
We also took sterilised water and kept everything (formula, water, baby food, medicines, sudocrem etc) in the infant carry-on luggage so that it was easy to identify for security when putting it through the x-ray checks.
We recently travelled to NZ, Australia and the Middle East with our two children and faced the dilemma of taking enough infant milk for the trip.
Our 3 month old is Lactose Intolerant and in the UK was prescribed Nutramigen, which is not available in NZ or the UAE. I had to pack tins and tins of it for our holiday which was a nightmare.
We were forced to find an alternative milk product in the UAE when our flight was delayed for 10 days!
I was amazed to see in the supermarket that Lactose Free (LF) infant formula was available in brands commonly sold in the UK - Aptimil LF, SMA LF etc, all readily available without prescription.
Naturally we tried the SMA LF as it was made in Ireland by Wyeth and now that we are back in the UK he is permanently on SMA LF, I simply order it from Boots.
Occassionally, Infant Formula providers have multiple products with different names sold around the globe (as I discovered with Wyeth). It is worth checking on their website to see if they sell your babies formula abroad, under a differnt name - to save you using up your luggage allowance!
Top Tip - Don't forget to declare your infant formula when you arrive at your destination. It can be easy to forget that it is a 'dairy product' which is on many of the declaration forms. The tins in your luggage should be sealed, only your carry-on tin should be open/used.
