geometry, i don't know if you've already taken your flight. i went through something similar last year, moving two cats across the country. the first step should be to talk to your vet - they may know if your cat has any special risk factors for such a long trip. if your cat is in good health, he may handle the stress of the trip well enough, but ask to be sure. i would also make a point of the fact that your trip is particularly long and punctuated by a long layover. you're looking at 10+ hours in a carrier, so sedation may be a realistic option.

my kitties endured 5.5 hours on the plane, plus an hour getting to the airport, roughly an hour waiting for the flight, plus an hour getting to their new home. my vet assumed - wrongly - that they would just sleep after awhile, but no, we listened to over 8 hours of uninterrupted miaowing. we did not have any accidents, but we did make sure to follow our vet's advice about withholding food and water before the trip.

typed with one of the kitties in my lap!