Separation of domestic and international departing pax

[Globaliser]

Originally Posted by deltahotel

Can't find a reference but I believe this is (within Europe at least) a Schengen thing. I remember being surprised to be mixing inbound and outbound at BRU, but it seems to be throughout the region.

It's pretty simple: passengers can basically be categorised against three criteria:

1. Are they inside or outside the relevant immigration border?
2. Are they inside or outside the relevant customs border?
3. Are they inside or outside the relevant security border (ie have they been acceptably security-cleared)?

Any passenger, whether arriving or departing, can safely mix with another passenger in the same category.

A passenger travelling from one Schengenland country to another Schengenland country is by definition inside the common immigration border at both ends (except in emergency situations). Most of Schengenland is in the EU and therefore inside the common customs border. By intra-Schengen arrangements, such a journey is also usually within a common security border. In most cases, such arriving passengers can therefore safely mix with departing passengers.

But sometimes such a journey will cross a customs border (eg EU --> Norway), so mixing can't occur until after the customs border has been crossed. And in most airports, you cross the customs border after you've had access to checked baggage, at which point you also cross the security border.