Adding the finer details.

When I was happy with the structures basic shape I then set about manipulating its geometry so I could create folds as well the complex cockpit at the top of the model. I primarily used the split polygon tool as well as the insert edge loop tool to create subdivisions that would help me later when extruding faces to create extra geometry in the form of rails and exterior details. To create the cockpit at the front of the model I literally drew out the windows using the split polygon tool whilst constantly looking at reference of airliners and oil tankers. The windows are very angular in appearance which is reminiscent of airliner cockpits. Once I had drawn out the basic shapes which would make up the cockpit I extruded the faces which would construct the windows back into the model. I was very pleased with the outcome as it gave the structure some character as well as function. I had the idea that the military could not only use this facility as a Chop Shop but as a overwatch point. To give the structure extra support I modeled a support beam to the rear which could also be used as a way of lifting materials into the core of the installation. I realised when modeling the cockpit that it would have been much easier to model one half of the structure then mirror it to keep the geometry clean.  I realised the mistake but decided to carry on as I was pleased with the way the model was turning out. If I was to do anything like this again I would concentrate on building half the object which would provide a cleaner model and cut down modeling time significantly.