Many airlines offer free in-town check-in services at Hong Kong and Kowloon stations on the Airport Express MTR line, allowing passengers to check in and check their bags at least 90 minutes and up to one day before their flight departs.
A Passenger’s Definitive Guide to Hong Kong International Airport (Chek Lap Kok)
Passenger's guide to Hong Kong International Airport - ground transport, airline lounges, hotels near the airport