Ryanair is an Irish airline headquartered in Dublin; however, its biggest operational base is at London Stansted Airport. It is Europe's largest low-cost carrier and it is one of the world's largest and most successful airlines (whether in terms of profits, number of flights, number of passengers flown). Ryanair operates—at one count[attribution needed]—on 460 routes to 25 countries. Ryanair has been characterised by rapid expansion, a result of the deregulation of the air industry in Europe in 1997. Over the years, it has evolved into one of the world's most profitable airlines, running at remarkable margins by passing its costs directly to its customers. Ryanair is the largest airline in Europe in terms of passenger numbers.