On Feb 22, 9:41*am, Roland Perry wrote:

Passport control is nothing to do with airlines.

Of course it is. If the airline flies someone who does not have the
credentials to enter the destination country, they get a hefty fine from
the authorities (as well as having to arrange to take them back).

If a passenger does not have the appropriate documentation he will not
be boarded that much is true.

However, airlines do not make the decision as to who shall or shall
not be admitted to any country. That is why you go through an
immigration procedure. Clearance by an airline for boarding does not
guarantee entrance at your destination.

If it's a low-cost doing a 25 minute turnaround, the plane will usually
be long gone by the time the passenger has "failed" immigration checks.

In which case the return flight will be fully boarded and probably
taken off before all immigration procedures have been completed with
respect to the previous incoming flight. There is no requirement for
them to carry out a refused entrant on the next possible flight which
might, in any case, be full. They do of course have to carry them out
eventually and no doubt there is a time limit but the refused entrant
will be detained until he is carried out.