The article is about having a completely separate plane (glider, really) that is towed by a conventional plane. The glider gets to ride in the powered plane's wake, and presumably the fuel cost to tow the cargo plane is less than the cost of flying two independent planes.
This isn't about making a larger conventional plane that has more volume to put cargo in.
Right, but if a plane has a maximum takeoff weight of 600k lb, I doubt if it can safely takeoff while being 600k lb AND towing another x00k lb in a glider, which is what would be required to reduce cargo costs by 65%.
This isn't about making a larger conventional plane that has more volume to put cargo in.