This report uses new econometric research and a review of previous studies to provide guidelines on the appropriate level and type of demand elasticity to use when analysing a policy proposal. It provides robust elasticity estimates to ensure that policy decisions related to issues such as liberalisation, airport charges, taxation, and emissions schemes, are made on the basis of appropriate and reliable evidence. It provides important new estimates to ensure that price elasticity estimates do not underestimate the sensitivity of passengers to price and are used correctly.Different air travel demand elasticities are associated with different uses. When consumers are choosing between airlines on a route, or even between destinations for travel, there is a degree of price elasticity for airline seats. However, if all competitors on a route, or if a wide range of routes all experience the same proportionate price increase, the demand for airline services becomes less elastic. As a price increase is extended to ever larger groups of competing airlines or competing destinations, then the overall demand for air travel is revealed to be somewhat inelastic