[1] Adding the overall details

After checking the overall drawing, I created a new layer to add details.

I added dividing lines, window details and frames.

 

[2] Adding sunlight

I forgot to add a sunlight effect so I will add it in this step.

Using the [Gradient] tool, I add sunlight by dragging from the sun as below.

I used a white color.

 

I lowered the layer opacity to 3% and the finished look is as shown below.

 

I added a small aircraft as well.

I adjusted the opacity of the sunlight layer to 8%.

 

I also changed the opacity of the aerial perspective layer accordingly.