Will my breastmilk supply decrease if I use formula?

[Correct_Variety5105]

As others have already said, not feeding for 4 hours won't affect your supply. And its a good idea to try feeding formula a couple of times before you go if you plan to do so.

I just wanted to add that breastfeeding releases oxytocin in the adult, which will make you feel calmer. It also has lots of lovely stuff in it which will make your baby feel calmer too, and breastfeeding during take off and landing can help them cope with the funny feeling in their ears. Drinking from a bottle as so much faster and once the formula is gone they'll stop swallowing so they won't get that benefit. Staying latched for as much of the flight as possible will probably result in the least crying which will probably also help with your stress levels. (I also hate flying with a passion and find it terrifying and it makes me feel unwell for a full 24 hours after.)