Hong Kong Airlines supports web and app check-in, typically opening 24-48h before departure and closing 45-120 minutes before (varies by airport and route). Confirm exact times on the official site.
After checking in online you receive a mobile boarding pass; checked bags must still be dropped at the counter before the cut-off. International flights usually require document verification at the airport, so allow extra time.
At the airline's home base (Hong Kong International Airport) you'll find the fullest set of counters, kiosks and bag-drop lanes; at peak hours (7-9am, holidays) arrive 30 minutes earlier than usual. Seat maps are widest the moment check-in opens — window, aisle and exit-row seats (sometimes paid) go first.
For international departures check passport validity (6+ months is the usual requirement) and destination visa/entry rules; some countries also require proof of onward travel, which the counter will verify.