The elasticity of air travel demand varies according to the coverage and location of the market in which prices are changed and the importance of the air travel price within the overall cost of travel. The appropriate elasticity to use will depend on the type of question being asked. What is the price that is being changed (e.g. an individual airline ticket price or prices within the market as a whole)? What is the unit of demand that is being assessed (e.g. demand for an individual airline or demand for total air travel)? Examining the traffic impact of a price increase on a given route requires a different elasticity than when examining the impact of an across-the-board price increase on all routes in a country or region.