You are allowed to bring water in baby bottles but show it when you board. So you are allowed to mix the formula before boarding. But your baby must drink it within 30 mn to 1 hour. Otherwise, it's not advised to mix the formula milk and the water. You can't keep it, even in a fridge. I've never had problem to have warm water to make the milk for my baby in a plane. I travelled short and long distance and always had the warm water whenever I asked for it, usually within 5 mn. And no problem for the temperature. Anyway, a baby can drink a cold formula milk. If you know what time is the feeding time for your baby, you can anticipate it and ask for the warm water when you know that the flight attendants are not too busy: usually, not when they are serving meals, not when the plane is taking off or landing. Otherwise, you just go to the cabin crew quarter and ask for some water. They will give it to you immediately.Thanks mummy ginko and mummy gumbokins. Really much appreciate your advices. From singapore boarding , am I allowed to make the formula first before entering boarding gate? Did thought of sourcing those liquid milk but I guess we can't carry in liquid too.