We just flew with a 6 month old. She didn't need much on the flight, but i packed for worst case scenario: brought extra toys, pacifiers, a change of clothes for both of us, enough formula for the day (after reading about a lady whose flight got delayed and was sitting on a plane all day). I bought ready to feed, that was easiest to fix on the plane without having to worry about the water being too cold for DD to drink. Wear easy to get off shoes, you'll have to take them off at security, take baby out of stroller/carrier, show your formula/milk - it was a little crazy.
We brought the umbrella stroller so we could use it in the airport and just in case something happened to it, it was cheap, unlike the fullsize stroller.
Call and see if your hotel has pack n plays to sleep in, that would save you bringing one.
If you BF, let your baby nurse during take off and landing. If not, give her something else to suck. It helps with popping ears. Also, if you are carrying her in a cling, wrap, or Bjorn, you need to take her out of it when going through security. You might want to check on liquids requirements at the airport before heading out also.
Re: Any tips for traveling with 4 month old?
We just flew with a 6 month old. She didn't need much on the flight, but i packed for worst case scenario: brought extra toys, pacifiers, a change of clothes for both of us, enough formula for the day (after reading about a lady whose flight got delayed and was sitting on a plane all day). I bought ready to feed, that was easiest to fix on the plane without having to worry about the water being too cold for DD to drink. Wear easy to get off shoes, you'll have to take them off at security, take baby out of stroller/carrier, show your formula/milk - it was a little crazy.
We brought the umbrella stroller so we could use it in the airport and just in case something happened to it, it was cheap, unlike the fullsize stroller.
Call and see if your hotel has pack n plays to sleep in, that would save you bringing one.