It obviously depends where you’re going but I’ve always found a good ‘cheat’ for Airlines is to layer up. 3 T-shirts, a hoodie and a coat is quite warm to wear but if it saves me a few square cm inside my carry-on for other things then so be it.

Also leave toiletries at home. Unless you’re backpacking in the Himalayas there are few places that don’t sell wash items and toothpaste when you get there.