Some airports experience significant congestion at least some of the time, where "congestion" means that use of the airport by one aircraft delays or prevents use of the airport in that time slot by another. Another way to say this is that airport access can be scarce. Virtually all economists agree that when a resource is scarce, it can be allocated most efficiently through the use of a mechanism that prices it to reflect its value to all other potential users. Theoretically, however, efficient prices can only be assured when both supply and demand are competitive, markets are complete (they allow purchases in any amount at any time), and the participants maximize utility by maximizing profit.
Michael E. Levine,
Airport Congestion: When Theory Meets Reality,
Yale J. on Reg.
Available at: http://digitalcommons.law.yale.edu/yjreg/vol26/iss1/3