Boston Airport Ruins

There’s another area in this location that can be entered from a blue door to the SW leading to Boston Airport Ruins. After going downstairs, you’ll find the elevator ahead of you. However, it requires an Airport ID so go to the right this time and open the double-door. Continue forth and anticipate ghoul ambushes.

In the first turn to the left, you’ll see a flooded walkway. There are hidden ghouls there so use your VATS to target them and kill them from a distance. Clear the path and use the broken ceiling as a ramp to reach the upper floor.

Follow the path and you’ll reach the parking garage. There are a lot of ghouls here so use explosives to detonate the cars and take out multiple targets at the same time. Fight your way deeper and you’ll finally see a working elevator. Taking this elevator will bring you to the surface, by the parking building near the airport. The entrance to the subway will be covered in rubble and can only be accessible once you have the quest “Duty or Dishonor” available.