i used to travel a lot myself with daughter on planes and more recently a 24 hour journey by car and boat myself with a 3 year and 15 month old
I would say for the flight, try not to worry about other folk around you as that gets you in a panic.
Locate toilet so you know where to go for any nappy changes, have everything in the baby bag to hand as it can be quite tricky to grab thinks
is she bottle of breast fed? make sure you have all thats needed for the flight if bottle.
I have 2 kids that dont like to be held so travelling on a plane or anywhere really is a stress
Hopefully at her age though, she might sleep through it all
If theres your son and his wife then one could hold the baby and the other take whatevers needed out the bag. it is handy to take 1 nappy, wipes, nappy bag out so its just in front of you
Also, will you have her car seat that you carry? Try and take the buggy straight to the plane. They normally take it right to the stairs/gate then you carry the baby from there. I once just carried the car seat forgetting the airport had been extended and having to carry that and the baby bag myself was a bit of a sweat
Is there any little finger foods she can have? Those organix rings or something like that might keep her occuiped. It just depends what the baby is like though. My kids have no interest in toys or anything so distractions is always tricky