NOTE ON THE ECONOMICS OF AIRLINE MARKETS
The purpose of this note is to provide background to the study of the airline industry by briefly discussing four important economic aspects of the industry: (1) the nature and measurement of airline costs; (2) economies of scope and hub-and-spoke networks; (3) the relationship between yields and market characteristics; and (4) the S-curve effect. The Appendix to this note contains a glossary of key terms used throughout the discussion.
Airline costs fall into three broad categories:
flight sensitive costs which vary with the number of flights the airline offers. These include the costs associated with crews, aircraft servicing, and fuel. Once the airline sets its schedule, these costs are fixed. traffic-sensitive costs which vary with the number of passengers. These include the costs associated with items such as ticketing agents and food. Airlines plan their expenditures on these items in anticipation of the level of traffic, but in the short run, these costs are also fixed. fixed overhead costs which include general and administrative expenses, costs associated with marketing and advertising, and interest expenses.
The largest category of costs is flight-sensitive. An important point about an airline’s cost structure, and a key to understanding the nature of competition in the industry, is that once an airline has set its schedule, nearly all of its costs are fixed and thus cannot be avoided. Because it is better to generate cash flow to cover some fixed costs, as opposed to none at all, an airline will be willing to fly passengers at prices far below its average total cost. This implies that the incidence of price wars during periods of low demand is likely to be greater in this industry than in most.
There are two alternative measures of an airline’s average (or, equivalently, unit) costs:
cost per available seat mile (ASM)
cost per revenue passenger mile (RPM)
Cost per ASM is an airline’s operating costs divided by the total number of seat-miles it flies. (An available seat mile is one seat flown one mile.) It is essentially the cost per unit of capacity. Cost per RPM is the airline’s operating costs divided by the number of revenue-passenger miles it flies. (A revenue passenger mile is one passenger flown one mile.) It is essentially the cost per unit of actual output. These two measures are related by the formula:
Cost per RPM = cost per ASM ( load factor
where load factor is the fraction of seats an airline fills on its flights. In the end, it is cost per RPM that an airline must worry about, for it must cover its cost per RPM to make a profit.
Airlines differ greatly in both their costs per ASM and costs per RPM. For example, in 1992 Southwest had a cost per ASM of 7.00 cents, while USAir had a cost per ASM of 10.90 cents. Similarly, Delta had a cost per RPM of 15.33 cents while American had a cost per RPM of 13.81.
Differences across airlines in cost per ASM reflect differences in:
1) average length of flights (cost per ASM declines with distance). 2) fleet composition (cost per ASM is smaller with bigger planes). 3) input prices, especially wage rates.
4) input productivity, especially labor.
5) overall operating efficiency.
Differences across airlines in cost per RPM reflect differences in cost per ASM plus differences in load factor. Two airlines might have very similar costs per ASM, but quite different costs per RPM because of differences in load factor. For example, in 1992 USAir and United’s cost per ASM differed by less than 2 cents (USAir 10.90, United 9.30), but their costs per RPM differed by nearly 5 cents (USAir 18.54, United 13.80) because of...