I check in a time bomb in a bag set to go off after flight leaves pine for Mumbai. Only way I can do this is to be traveling to Mumbai. However, I don't wish to die, so I try to get off in pine. Hence the check. Also the pax remaining on board are also counted, just in case someone pays dxb pnq fare and decides to take a chance and continue onwards to mumbai.

Or the third case where the pax is a stupid clueless idiot, who has no clue what happening around him , is not listening to the announcements and gets confused where he I and where he has to go.