I need a keycard for one of the elevators and I can't use the Workshop yet, is there a quest involved?

I stumbled across the airport it by accident. Not sure if its quest related, I think if you look around you'll find what you need.

I do believe it's BoS friendly-required (with the prydwyn being so damn close to it and all).

I did some searching and it's quest related so gonna go look where I can find that quest, it would be quite a fun place to make a settlement.

Don't get your hopes up. This settlement is of very limited use.

the Boston Airport workbench is where you build the.. machine.. if you choose to get the Brotherhood to help you. It's pretty much locked to the Brotherhood until they win or lose.

AFTER you finish the main quest, you can use the Airport as a regular settlement and build houses etc

Damn, that's cold.