RouteLevel. The review of previous research found route level elasticities ranging from -1.2 to -1.5. Regressions using the US DB1A data, which allows the use of route dummies and variables to capture the price of route substitutes, produced a similar air travel price elasticity of -1.4. This elasticity estimate is applicable to a situation where the price of an individual route changes (e.g. higher airport charges at Paris CDG raising the price of travel from London and diverting leisure traffic to another destination, such as Frankfurt). Using distance as an instrument variable within the 2SLS (Two Stage Least Squares) statistical model produces results that further support this elasticity, though there still is some concern over the use of distance in this way due to its perceived exogenous influence on demand.