> However, in a typical overbooking situation, there are more passengers than seats, so it's unclear who the buyer and sellers are The passengers with tickets

> However, in a typical overbooking situation, there are more passengers than seats, so it's unclear who the buyer and sellers are The passengers with tickets are still sellers in your second scenario; to the airline as a buyer. The airline needs to buy back the number of seats that they oversold for which passengers checked in.