are the two oldest reports that I could find of someone actually getting to
the very bottom of the shaft:
from the bottom of the shaft can
be found in the HBO Tricks section. Ziga writes:
Hud and Ziga discover that its possible to get back into the pelican that
initially drops you off at the start of assault on the control room. Many
interesting places can be reached after that, and to our surprise its
possible to flip the pelican as its flying causing it to crash into many
walls and bump around. If you time it perfectly you will make it all the way
down into the pit and walk around in a blue fog.
how to do it:
Play co-op in Assault on the Control Room. Have both players press x to
enter the pelican as soon as they begin to jump out.
After the screen begins to turn blue, have one player jump out and hit the
X button repeatedly to flip the Pelican.
it! When the player flips the pelican after it has started to turn over
(but before both players are ejected) it allows one player to remain seated in
the pelican... and the pelican won't vanish.
a player in the pelican is easy... the hard part is timing the flip just
right so that the pelican falls all the way down to the bottom without
getting stuck or flipping the remaining player out. I suggest trying
to flip it several times when the player jumps out, by pressing X very
quickly. This helps the pelican fall flat and upright.