I have a confirmed CW ticket on BA28 flying out of HKG to LHR tonight. Online check-in has been unsuccessful all day. I phoned BA HK call centre for that matter. I was told that the flight would be on schedule but is quite full so some passengers might not be offered online check-in. Airport check-in is the only option. What does that mean? What could happen to me? Should I go to the airport as early as possible to make sure I could fly as scheduled?