Breastfeed and formula feed?

I have a 1 month old bby boy, he has been breastfeed since he was born and still is. We are flying to tn for 3 weeks to meet his daddys family, anyway im wondering can i formula feed my bby when flying and everyonce and awhile when we are out doing running around, and then breast feed at night or when home? i dont want to take him off of breastfeeding but pumping is hard to do exp since he eats alot also i dont like having to breastfeed in public. please help!!