LCCs now account for about a fifth of all flights globally, making it increasingly vital for airports and air traffic management providers to understand the sector and its drivers. Worldwide, of the top 20 airports for LCC aircraft movements, 12 are in the US, four are in Europe and the remainder are in the Asia Pacific region. (By seats, ten are in the US, and five each in Europe and Asia Pacific). As ever, though, the global LCC market is in flux. Airlines expand or contract their operations at airports in relation to their own growth trajectories and the changes in season.