Hangar

 http://www.notarealthing.com/2010/09/skyfleet-and-texron/

Create cube

Add resolution using connect, pinch + inset

Select polygon + indent as shown below

Select roof - extrude - 

Add geometry along roof using connect

Manipulate vertex to create curved roof

Creating roof inside

Create cube - change dimensions to slim cuboid - array for depth

Select all duplicates - tools - array - second direction

Create connecting beam (cube stretched) array in two directions at once (to connect all components of inside roof)

Third connection slopes to towards centre therefore requires two directional array to mid point

Then mirrored to complete

Move into position

Attempt 2

Walls - features

Create gengon - 6 sided - to taper

Clone and place into pattern as shown

Connect gengon's using bridge (select opposing polygons, bridge tool)

Extrude further as shown

Attempt 3

Before connecting using bridge - inset every side to give extra detail to joining parts

Extrude and connect as shown (shown next to previous attempt

Place onto wall - extend horizontal  shafts - add extra cubes (cuboids) for detail

Replicate main feature of wall to add detail

Mirror to cover opposing wall

Back wall - cubes - stretched - inset one side - move ploygon in for indent as shown below - pair with clone - replicate across the back wall

detach roof - clone - place next to original

Select outside wall - extrude to line with roof

Crane

Create gengon -  6 sided - no taper - select bottom face - inset - extrude + repeat 5x

Create cage using same technique as cage for truck roof

Cube - inset all sides - remove unneeded polygons - bridge created gaps