Little ship, opl Barnard Xylophis short range shuttle

[nozmajner]

You just join up all faces to an ngon with F, then put back edges where needed, by selecting two vertices and pressing j.
Like this.

[Nyankosensei]

i have used modifier decimate with planar and work fine

P.S.
I think is right what you tell about the model, starting right is the best way for learn right

[nozmajner]

I never trust the decimator really. Or the booleans or the auto UV. They need too much cleanup. :)

[Nyankosensei]

decimator seems work fine, i don't like booleans too but this function is nice for merge faces