No, not an Island term. But it's just what is said at Delta when multiple pilots want the JS. They "flow through" the cockpit to a seat in the cabin. The term isn't as relevant as having a JS reservation and getting bumped off the plane by a Flight Attendant or anyone else for that matter when seats are available. Sorry the "flow through" term is causing such an issue. Let's call it "getting a seat in the back" from here out then.