Apparently, a minimum of 45F. I am about to send my Westie LHR-IAH-RSW, and am assured she will be "very comfortable" - to include "special assistance" at IAH if temp. exceeds 85F!

BTW, she (or rather I) even gets miles, but sadly, at the rather measly rate of 1 mile per $1 of cost (although it ain't cheap to send a dog TATL).

And, she won't even get the IFE, but I hope she gets some decent in-flight service. If so, she will almost certainly go for chicken rather than beef, which will keep her happy for a few minutes at least.

Just hope there are no WX problems for her at IAH. Apparently, customs clearance for "alien" pets can also take a few hours, so it'ss going to be no fun at all for her first flight.