Originally Posted by LHR/MEL/Europe FF

Delays happen on the day - usually ATC driven although weather is sometimes a contributing factor.

The delays are rolling... it's usually every flight that gets pushed back, not just one or two.

Delays can either be once you board, or you can be delayed in the departure gate. If your inbound is three hours late, you'll be three hours late leaving.

However... because CX/KA have so many flights, if you get out to the airport early enough they will put you on the next available flight... which is fine, unless peak periods when everything is full.