But KLM (Dutch flag carrier) found a way around that: if a flight is overloaded by weight they will keep all the passengers on board but leave their luggage behind. There is no direct penalty for late luggage, so many customers will get nothing except perhaps a little free shopping if they feel like filing forms to reimburse for having to buy clothes at their destination. But that's cheaper than the penalty for not taking the passenger on time, so KLM "optimized" it.