Hint: Combinatorics Q2

What is the maximum number of airports we could reach in at most two flights from a given airport?

That implies the maximum total number of airports is?

Can we arrange things to work for this maximum? (Hint: No -- the situation is too tightly constrained, but figuring out the exact blockage will require a little work. Start drawing networks!)

What if we reduce the number of airports by one? (And aim for some sort of symmetric solution?)