I took two international trips with my now 3yo, one to Thailand and one to Bali, when she was one 1/4 and one 3/4. She was pretty happy both trips except some of the longer flights. I decided not to do longer flights while she is toddler age, so we have only done domestic trips this past year, and fortunately she has been pretty good, but I do centre everything around her, and I’m a single parent. I’m waiting till she is probably or 5 for anything longer now, and can recommend the book Hunt Gather Parent for general parenting advice, though the style is a bit annoying I think a lot of the advice is sound.
I tried to do EC (elimination communication) but wasn’t super successful, but it did mean my daughter was very used to sitting on a mini potty regularly well before we did “proper” potty training with big potty. About a month before 2nd birthday got a book about potty training from the library, and then spent a weekend pants free, and she got it very quickly. Got poops a lot faster than pee though, she only had maybe 2 poops in a nappy after her 2nd birthday, but I had to keep putting nappies on for longer drives or trips because she just wouldn’t tell me she needed to pee. She was pretty much fully toilet trained by 3, but has had a couple of accidents, 2 bed wetting one end of day at childcare. Not sure about those but not too worried about it.