Originally Posted by
Aus_Mal
The airline knows who is onboard and their passport number is recorded on check-in. So they can hand that printout and data to Immigration.
They can then match people with their passport numbers (and visas where appropriate) on the system etc and possibly process them that way.
It's not like people purposely hop on a plane hoping it will crash, so I see this situation as not too different from your baggage being allowed to fly on a separate flight to you if it gets lost rather than the usual rule of positive baggage matching.
However, checked luggage reclaim is normally after immigration. People without visas on connecting flights cannot get at checked luggage. So, it is natural that identity documents should be carried into the cabin.
Some people are alleged to have maliciously destroyed their own identity documents while on a plane. Supposedly with the aim to hinder being sent back. Not sure where it is supposed to work... Certainly, pickpockets might operate aboard a plane, and steal valuables, cash, cards or identity documents whether from hand luggage or from pockets... but is it practical to get away from the scene? If a passenger who probably must have presented ID at check in arrives and claims to have had the ID stolen while in flight, would the passenger be believed and all other passengers thoroughly searched? Or would the passenger be disbelieved and thought to have destroyed his or her own ID deliberately?