In some countries it is not illegal for a company to drive away competitors by selling a product below cost.

Airline executives generally believe that a company that once underpriced its fares to drive away competitors is very likely to do so again if new competitors emerge.

As part of promotions designed to attract new customers, airlines sometimes reduce their ticket prices to below an economically sustainable level.

On deciding to stop serving particular routes, most airlines shift resources to other routes rather than reduce the size of their operations.

When airlines dramatically reduce their fares on a particular route, the total number of air passengers on that route increases greatly.