High-speed rail competes with flying on journeys of roughly two to four hours. Below that, ordinary trains are already quicker from door to door; above it, passengers return to aircraft however fast the train. Within the window the effect can be dramatic: on several European routes the airlines withdrew within three years of the line opening. This explains why high-speed lines are built between large cities a few hundred kilometres apart, and why proposals to extend them into thinly populated regions rarely survive scrutiny.