Hi Heather,
I used to bring clean empty bottles and ask the air hostess to fill one with warm water for me when it was time for a feed - they have hot water coming out of a coffee machine type thing, no microwave (at least the times I flew) so no point asking them to heat cold water for you that you buy in a bottle as I don't think they have the facilities to. If you know you will need to feed your baby between checking in and getting on the plane though I would suggest pre-filling a bottle with warm water already and keeping it in a bottle warmer though you will probably need to take a sip of it when you go through the security checks to prove it isn't a bomb!
Good luck, it sounds daunting I know but keep him happy and full and it should fly by.. you know about giving him something to suck during take off and landing, right? It helps their ears - just water will do if it's not time for a feed and you don't want to disrupt his routine
Also some people might advise immediately switching to the new routine (in the new time zone) when getting on the plane but to be honest flying with a baby is stressful enough as it is so just stick to what he knows and deal with the jetlag when you need to..
Good luck!
Sue x