A civilian airport is huge both inside, has hectares of land area and thousands of staff.

Given that this never happened to before, requires sneaking thousands of armed men into to USA and does not achieve anything obvious besides general terrorism, why do you believe this is relevant?

And if someone did commandeer an airport, why would you evacuate the president instead of putting him in the panic room and flooding Washington with military and police?

I'd note that it has absolutely happened.

https://en.wikipedia.org/wiki/Entebbe_raid

Oh common, Israel vs Uganda?

> The entire operation lasted 53 minutes – of which the assault lasted only 30 minutes

They did not even control of the whole airport, let alone for a prolonged period of time. they got the hostages out and GTFO’d.