Short-Haul vs. Long-Haul Travel. Price elasticities on short-haul routes were generally higher than on long-haul routes. In part, this reflects the opportunity for inter-modal substitution on short-haul routes.
Airline vs. Market vs. National Elasticities. Some of the studies supported the concept that the demand elasticity faced by an individual airline is higher than that faced by the whole market.
Income Elasticities. Including income as an explanatory variable of demand isolates the effects of a shift along the demand curve (caused by a change in air travel price) from the effect of a shift of the whole demand curve (caused by a change in incomes or GDP).