Price Class Level. This the most disaggregate level, •where passengers make a choice between different price classes (e.g. first class, business class, economy class) on individual airlines.Airline / Air Carrier Level. This reflects the overall •demand curve facing each airline on a particular route.Route / Market Level. At the route or market level •(e.g. London Heathrow–Paris CDG or London–Paris), travellers faced with a price increase on all carriers serving a route (e.g. due to an increase in airport fees and charges), and have fewer options for substitution. National Level. At the national level, travel prices are •increased on all routes to and from a particular country (e.g. due to a higher national departure tax), giving travellers fewer options for avoiding the price increase. Supra-National Level. This represents a change in •travel prices that occurs at a regional level across several countries (e.g. an aviation tax imposed on all member states of the European Union). In this case, the options for avoiding the price increase are even further reduced