Giger's Egg Silo and the Derelict squeezed into one

leading from: 
The Space Jockey's Story
and

  The design of the derelict

a.) Wrecked Construction Of Non Human Manufacture 
Originally in the alien script, the men discover a crashed derelict spacecraft and they enter it and discover that the alien occupants are all dead. They return to their own ship to contemplate what may have killed the alien crew and then they discover a pyramid on the plant which appears to be indigenous and it's primitive. 

They enter the pyramid and there they find the eggs. In the movie, the Earthmen discover what Dan O'Bannon would refer to as a "wrecked construction of non-human manufacture" that we might assume is the remains of a space craft, and inside they find the eggs of the monster. but following Dan's point of view, it was no long easy to say what it was

Concept for egg silo exterior

b.) Two Elements Squeezed Into One Sort Of Uneasy Entity.
Giger was brought in to design the pyramid and soon the derelict ships. The pyramid idea had given way to an extraordinary biomechanic breast shaped silo, still with the exterior and interior designed by Giger. Since the derelict and the silo both followed the biomechanic design of Giger, and budget cuts were necessary,  further budget cuts took place and the two elements were merged together as if the silo were connected to the space jockey chamber from below the space jockey platform. 

So what was it now, a space ship that landed on the surface or did it have a major part of it somehow buried beneath the ground? Special effects technician Jon Sorensen on the set recalled that they felt that there was more of the Derelict buried under what was seen, it was just an opinion but Kane being lowered down to the egg chamber showed that.

(detail ) Giger's sketch for the space jockey with silo entrance and  silo

c.) Derelict Ship Infested By An Insect Nest Alien
The derelict that was once a space ship seems no longer to be a space ship, we can't say what it is, no one can make a direct claim. However Giger conformed to the ideas of the initial story though about the derelict having been infested by aliens. It was as if the derelict space ship had landed on an anthill and the ants had eaten their way through the spacecraft like parasites in order to use the pilot at a host. And soon the eggs would also be considered something layed inside as termites would do within the wall of a house.

(detail ) Giger's sketch for the space jockey

Source Quotes

1. Dan O'Bannon: In the movie, the Earthmen discover a wrecked, derelict spacecraft, actually no, that's not correct. In the movie, the men discover a wrecked construction of non human manufacture and inside of it they find eggs of the monster. In the original script, the men find the crashed derelict spacecraft and they enter it, they discover that the aliens are all dead. They return to their own ship to contemplate what may have killed the alien crew and then they discover a pyramid on the planet which appears to be indigenous and it's primitive. They enter the pyramid and there they find the eggs. (Fantastic Films 1o, p29) 
2. Dan O'Bannon: They combined these two elements, they squeezed them into one sort of uneasy entity.
   Fantastic Film: The idea behind that, I would assume, being that the dangerous aliens were coming back to spawn.
   O'Bannon: No, they were two different races. In my script, it was a space going race that landed on this planet and had been wiped out by whatever was there, And now the Earthmen come and endanger themselves in the same way. In the new version, it's just a sort of a surrealist mystery.  (Fantastic Films 10 p29-30) 
3. FX: What is the relationship between the Space Jockey and the Alien Eggs?
   HR Giger: They always told me that the Space Jockey was another alien race, so he is not part of the Alien or the Eggs. To save money, the Egg Chamber and the Space of the Egg Silo were the same . The inside of the Egg Silo were elements of my painting, and was actually the entrance to a round silo which ended up in another set. (FX, 7, 1999 (spanish magazine0 
4. H R Giger: The egg silo and the space craft are now joined together, i.e. the astronauts enter through one of the three sewers, wind their way through the snail corridor, and find the corpse of the pilot which is twice as big as a human. Next to the seat of the pilot, there's a hole that leads into the depths of the silo.(The whole thing has been changed because the exterior views of the silo would have been too expensive!) So the silo was placed under the spacecraft, as if a mini UFO had landed on an anthill, and the ants had eaten their way through the spacecraft, like parasites, in order to use the pilot as a host. (Undated, perhaps around March 1978, Giger's Alien Diaries, p155, translation of p11, published 2013)
5. H R Giger: Since the producers have now decided that the eggsilo is to be an integral part of the derelict, the shaft now forms a direct passage from the cockpit to the eggsilo.(27th June, 1978, Giger's Alien, p34)
6. H R Giger: The broken floorboard, which looks like a turntable, is some 1.50 metres (five feet) above the floor. In the original script the egg silo was immediately below the cockpit , so that one of these holes in the floorboard acts as a way down for the astronaut unto the regions below him. (25th July, 1978, Giger's Alien, p34)
7. H R Giger: We decided that it would be a good idea to have these eggs inside the derelict like termites within the wall of a house. (CFQ vol 9, no 1)
8. H R Giger: So we designed another silo but then the budget wasn't big enough to include this structure so we decided it would be a good idea to have these eggs inside the derelict like termites inside the walls of the house. ( Warren Presents Alien collectors edition, p 31)
9. Jon Sorenson: we always felt that there was more of the Derelict buried under what you saw...Kane being lowered down to the egg chamber showed you that. Just our opinion at the time. (Facebook , June 12th 2014)