Estimates of national elasticities using all three datasets found that, without the route substitution term, elasticities fell to around -0.8. This inelastic result was found over a range of model specifications which excluded route dummies. The national level elasticity applies to a situation such as the doubling of a national passenger departure tax, affecting all departing routes equally but leaving the cost of travel from elsewhere unchanged. Its value reflects a combination of the route own price elasticities with cross price elasticities, when all national routes have prices which vary in the same way. The inelastic result is consistent with observations that part of the price elasticity observed from low cost carriers (LCCs) involves substitution from other routes. When this is controlled for, LCCs have a lower level of market stimulation, consistent with less elastic national elasticities.