後備機位使唔使加錢?

Basically, you show up at the airport and go to the check-in counter and tell them you want to standby.

They will let you know how to do it.

It is possible that you may have to pay a large amount (or maybe nothing) - it all depends on the airlines' policy.

2011-02-11 00:38:11 補充：
Tell them the magic word - "Standby"

不用，即使是由經濟客位轉商務或頭等都不用加錢。