Best advice I’ve heard is to set your watch for landing time as soon as you board. Then basal and bolus based on that. I don’t pump, but if I did I would do the same with my pump. I tell them not to collect my tray if I’m not ready to eat - just save it for when you want to eat.
I always find that I am much more active when I arrive, especially at first, so be prepared to take less insulin (so for example I would take one fewer basal doses instead of one extra when I changed the five hour timezones to Europe). Be prepared to adjust your insulin - I find I always need to.
I pack the insulin and supplies that I will need plus some extra on my carry-on baggage. And I put the rest, more than enough of everything to cover my full trip time including plenty of glucose tabs or equivalent, in my bag. You certainly can buy anything you need while traveling - probably for far less than it costs here thanks to our wonderful health care system - but who wants to spend time finding a doctor and pharmacy when you have limited time. I spent a month in Japan a couple years ago and made sure I had plenty of supplies due to my language barrier - insulin kept fine in my hotel fridge.
One other bit of advice (which I never needed to use but that made me feel more comfortable) - look up how to say “diabetes” and “please help me” and “I need sugar” in the native language of whatever countries you’re going to. Tokyo is easy, but I was also wandering around rural parts of Japan where English was definitely not well known.