Taking my 3 month old on their first plane trip

My family is taking a trip to see my grandma this weekend and we are taking my 3 month old. Once we are there, they are set up with cribs and such since my family down there recently had a baby as well. I’m wondering what kind of stuff you found helpful to have in the airport/for the plane/ and while you were on your trip? The trip is 3 days including travel and we are staying in a hotel. We formula feed so I need to consider how many bottles to pack/how am I going to clean them???