As you try to make your way to the airfield for the first time a haunted truck tries to run you over inside the tunnel. You then remember Amelia once saying:
“I like that you’re a mechanic, Wilson. There’s just something about a man who knows his way around a garage…”
You must go back to Bastion Falls. Behind the Golf filling station is a can of oil. Bring that back to the truck. When it tries to run you over again do the correct swipes on the screen and it will throw the oil all over the ground. This will cause the truck spinning out of control into a neerby ditch. You may then pass into the airfield.