Comment by rafram

In the US, generally one hour no matter whether it's domestic or international. In Germany, like three hours because security and immigration is insanely slow and inefficient. In the UK and other countries I'm less familiar with, two is usually fine.

If I come earlier, it's with the expectation that I'll waste some time hanging out in a lounge.

(Train situation is similar in the US, in places where we actually have those. Generally fine to show up right before departure.)