Bender flew from Vienna to Florida about a month ago. He did surprisingly well without drugs
I would attempt to potty between the flights, and bring a piddle pad or something in case he gets whiney. Then you can sneak him into the bathroom and let him walk around a bit and potty. Other than that, you'll be doing a lot of talking and soothing through a carrier most likely
I stuck my fingers in every once in awhile, and it calmed Bender a lot. He was very good most of the flights, though he was really whiney on the up and down portions, I think the pressure change hurt him a little.