How long they've been in the bunker keeps changing in different conversations on the same day. In the opening voiceover, Dominik says it's been 9 days. At breakfast, the soldier says Ines has talked about a party for weeks, and Ayaz also talks about weeks with Lom. Later, Laura tells Horst while they're dissecting the rats that the results have been the same for months. But when they find Terenzio's body, there's no way it's been exposed to the elements anywhere near that long.
Inside the building is not Brussels Airport nor the tarmac is Brussels Aiport.