[atoav]

So how long before the actual flight departure will you be at the airport?

If I catch a train that is 10 minutes before the train departs on a metropolitan train station in Europe.

With planes in my experience arriving two hours before the actual departure is not uncommon at bigger airports, since there are more insecurities involved like how crowded security checks are, where your gate is, etc.

[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.)