1) Desaturate.
2) Up the contrast.
3) Add glow.
4) Add more searchlights!
(A friend of mine who was a compositor on Sky Captain said that "add more searchlights" became a running joke with the director, because he took the position that more searchlights would always be better.)
Also note that some of the darker areas seem to bleed a bit into the brighter areas, which used to happen a lot in printing negative film before anti-halation coatings became common. You can get that effect by inverting the image, converting to Lab color, applying a glow effect in luminosity, converting back to RGB, and then re-inverting.
-- Mark