Tomster - I travel quite a bit (I can fly for free) and have taken many long haul flights. Went to Bali in Feb which was about
24 hours of flying in total. Australia a few years ago, also about
24 hours of flying (with stopovers).
I always take Gax-X before I leave - strangely enough I once had gas trapped in my gut and had alot of pain on landing with the pressure! Never would have thought that would happen but I guess if it can cause pressure in your sinuses why not in your colon, right?
I also always bring plenty of snacks with me - food I know won't make me sick. I always pick 'safe' plane food when they serve meals - whatever the safest option is and I don't eat anything that looks 'suspicious'. I also always make sure I'm hydrated throughout the flight - even if it makes me use the restroom more. One very important thing I remember to do is take my medication regularly while on the flight and make sure its still spaced out evenly even with the time changes.
I find the drastic time changes to be what screws up my UC the most - not getting good sleep on the flight, my sleep pattern being off when I arrive at my destination.
Sleeping on the flight definitely helps - from Narita to Singapore in Feb I was lucky to have a row to myself and slept almost 7 hours. That really got my energy back up when we arrived in SIN. But I didn't sleep much on the first leg from the US to Japan and felt pretty crappy when we landed. I do take Melatonin on the plane if its an overnight flight and it does help me sleep.