We've had a few long haul flights recently and it really is manageable. I'd say 1 or 2 favourite toys/books is enough from my experience. Fdefinitely try to get a cot. And definitely a sling, we needed it to get him off to sleep a couple of times when the flight times didn't work out. We took ready made milk and went prepared to pour it into bottles although we didn't need to, I did have to taste the Ella's pouches though, sadly not the flavours I would have wanted to! Only other advice is that it can be both very cold and very hot on a plane so simple layers work best, we had him in pjs mostly with a jumper and a blanket as extras. If your baby is the one that cries, try not to worry. You need to focus on the baby and either people understand or they don't, and I don't think you can do anything to change that!