Apologies if this question has been asked already, or if I'm posting this in the wrong forum, but I've always wondered how BA is able to offer hand luggage (both carry on + personal item) at up to 23 kgs each, whereas other oneworld airlines (*cough* Finnair, Qatar, even Iberia sometimes) are extremely strict about carry on limits. Despite better service from carriers like QR, I will go out of my way to fly BA because I know I don't have to worry about my carry on weight. Obviously more weight = more fuel = more costs, which explains why airlines like Finnair have started to crack down. How does BA account for this variability in hand luggage weight when it comes to flight planning? Why doesn't this extend to IB?