Delta owns T2 (from National via PanAm) and owned T3 (via PanAm). I know that this isn't the cooperative thing to do, but T1 is in a bind - yeah they want to expand, but Delta could work with T4 to expand into the T3 area (not sure if the land is still DL land or how that works) and use T2 to block T1 until they get what they want to the point that T1 has to live with what they've got.