There are a few reasons due to which Delta Cancel flight reservations of travellers who had booked their flight late. One of the main reasons for this is overbooking. Usually airlines accept reservations more than the number of seats, the reason behind that is, a lot of people cancel their flights, so those seats get filled later on. However, in such circumstances where no or very less number of travellers end up cancelling, the Airlines has to remove some passengers from that flight.