Most airlines offer frequent flier mileage awards where a passenger who accumulates enough miles can turn those miles in for an airline ticket at very little extra cost.

How should the airlines handle the accumulated mileage at the end of each year?

If you believe there should be a liability established; why is there a liability, when should it be booked, how many dollars should be booked and what type of liability is it (determinable, estimated or contingent)?

Please identify the additional costs to the airline for a mileage ticket What is the source or support for your answer?