Hong Kong reduced rail and bus links to the city’s airport on Sunday and police stepped up security checks in a bid to scupper plans by pro-democracy protesters to disrupt the bustling transport hub. The airport — the world’s eighth busiest — has become a frequent target for a protest movement pushing for greater democratic rights and police accountability. Online forums used by the largely leaderless movement had called for a “stress test” of the airport on Sunday, code for disrupting travel links or occupying buildings.