The film is based on a series of novels by Hiroshi Mori and takes place in a quasi-alternate version of Europe. The reason I say "quasi-alternate" is that even though many of the film's locations are recognizable, the setting is intentionally vague and, like much of the film, invokes ideas and feelings of real places (like the always-clouding skies over Poland) rather than pointing out specific locations.
The plot follows Kannami, a new pilot for Rostock, a corporation that manufactures airplanes and related weapons. Like the rest of the pilots, Kannami is a Kildren, a race of humans bred as soldiers for Rostock's war against rival corporation, Lautern. Kildren never age and, it is suggested, could live forever were it not for the constant combat. Kannami was brought in to replace Jinroh, who may or may not have died in combat. Kannami's presence strikes a cord with Kunsanagi, a pilot who has managed to make it through seven years of wars and have a child (whom she refers to as her "little sister").
If my description of the plot sounds a bit directionless and scattered, it is by intent. The Sky Crawlers is a very methodical film; while it doesn't seem like much goes on throughout most of the story, a whole lot is actually happening. The first hour or so feels like a collection of random plot threads, but once the first knot is tied, everything comes together. I enjoyed this, but it also requires the viewer to pay close attention to everything. Even throwaway comments are incredibly important to the overall picture. There's a lot going on at all times, which works both to the film's advantage and detriment.
During one of the features, Oshii admits that he went for the most realistic, yet stylistic visuals he could muster. There's an eerie sense of detail throughout the film that places emphasis on smaller "ticks," not just larger movements. The style creates an odd feeling that ventures into new parts of the uncanny valley. While not completely realistic visually, character movements are beyond perfect and catch even the most obscure of muscle twitches. As a result, characters feel like zombies, tying into the film's idea that the characters are little more than soulless pieces of hardware. This is hammered home by the incredibly detailed planes, building on Oshii's overall notion that technology is becoming more real that people.
If you aren't able to pick up on Oshii's overall thesis during the film, the included documentaries will clue you in. One covers the real world scouting, while another looks at sound and animation. Both emphasize the amount of detail found throughout the film and are required viewing for animation fans, or anyone interested in the process. Finally, there's an interview with Oshii made up of several interviews. The constant jumping between settings and camera types is jarring, but the interview is informative.
The Sky Crawlers is more of an intellectual film rather than an action-packed anime. If you're the type of viewer who needs a lot of action, The Sky Crawlers won't deliver. There are a couple of great dogfight scenes littered throughout the story, but even these seem to drag on a little longer than the expected norm. At the same time, viewers who enjoy picking out details and piecing them together will come away happy.