Over the last twenty years, airports and airlines have been privatised in a number of countries. However, many of the fundamental functions of airports remain outside the market process. In particular, the allocation of take-off and landing slots is largely determined by custom and practice and by regulation. The pricing of such slots does not follow economically rational principles. The current, arbitrary system of allocating airport slots can hinder competition and prevent slots being used by airlines that value them most. The authors suggest how a market in airport slots can be developed to address these problems. They are careful to take account of competition issues and other special features of the industry in developing their proposals. Nevertheless, the authors agree on the need to assign property rights to airport slots and allow slots to be traded. Only then can there be a more rational allocation of scarce airport take-off and landing slots.