I knew there was something I was to pontificate about on the internet tonight!
Like Issue 2, we've got a fictional and a real-life set of references merged in together. Here, the real-world elements are post-WWII rocketry and the conspiracy theories that surround it. The US government did indeed extract Nazi engineers and scientists from Germany as WWII came to a close, but the idea that they ran a secret second space program is pure conspiracy theory. NASA ran no manned military flights during the 60s and 70s, though there were 10 shuttle missions between 1982 and 1992 that have fully or partially classified Department of Defence payloads. The closest thing to actual conflict in space was when the Russians test-fired a cannon in orbit in 1975.. The Russian SSTO seen on a launchpad in one slide is a reference to the Buran, their failed (in our world) equivalent to the Space Shuttle.
The fictional reference is, of course the Four being analogues for the Fantastic Four. Randall Dowling being described as a polymath is a clear reference to the stereotypical super-scientist in SF who can apply themselves to any field. Four Voyagers Plaza is of course a reference to Four Freedoms Plaza (and by extension the Baxter Building). The Subterrans are the Moloid servants of long-time FF enemy the Mole Man, and the universe in a frame that Jakita and Snow walk past is a portal to the Negative Universe.
Moving on to the actual story, we're into territory similar to issue 2 and 3 that we get a lot of setup and reference, but then the story just stops. 10 pages of the issue are not part of Snow and Jakita infiltrating the base, and of the 12 pages of infiltration, 4 are them getting to Dowling's lab. And one of those 8 pages has dialogue from Drums' briefing in it. It's a very packed issue and the end suffers a bit from it.
While I'm here, I'm going to talk about the end for a bit and then loop back. Because it's also the end of the beginning for Planetary as a comic. Leather's line "We're adventurers, my crewmates and I. On the Human adventure. And you can't all come along" is the core of the conflict that will define the remaining 75% of the book. The reason we got Snow becoming proactive at the end of issue 4, and his suspicions about Planetary's agenda in issue 5 were to inform why he's so angry about the Four here. Snow is part of the Earth's defence mechanism, he's there to uncover mystery and bring it to light. The Four want to monopolise that same mystery for their own gain. These are diametrically opposed viewpoints, and Planetary and the Four are on a collision course. This is the end of the first trade paperback (excepting the bundled preview), and it's a great narrative halt. Around the World and Other stories sets up Planetary, informs us as to what Planetary does, tells us who our protagonist is, and then gives us an antagonist. By the general rules of storytelling the introduction is complete, it's on to rising action.
And so, as Ellis has given us elements of Snow's personality in the last two issues to set up his vehemence here, Leather delivers Snow's motivation towards the plot of the second book: "I've known you for far too long."; "Do you really not remember us? Who benefits from your lack of memory? Who knows the secret history of Elijah Snow? What are your teammates not telling you?". It's not a secret that the second trade is called The Fourth Man.
From a technical standpoint, this is another issue that's firing on all cylinders, Cassaday uses splash pages to great effect twice- the extreme closeup (WOAAAAAH! YEAAAAAAAH!) of an eye with the snowflake reflected in it as the first page, and then by contrast a shot tall enough to show the portal to another universe to the point that Jakita and Snow are tiny figures at the bottom of the page. There's a few other great uses of perspective to denote power in the issue - Snow and Jakita shot from below as they enter Four Voyagers Plaza. Again, compare these shots with Snow looming over Leather as the former rants and the latter recovers from his bollocks-kicking. Also in that shot the window that was smashed when Leather defenestrated Jakita is back in place, showing that what happened a few panels earlier doesn't even matter.
In other art awesomeness, the tight closeup on Jakita and Snow's faces as the lift doors close, their eyes in shadow sets the mood brilliantly, another example of Cassaday's use of strong inks when necessary. And that rocket behind the Four in their group shot looks like a baroque version of a filtration device I used to use in chemistry class but now it's a spaceship! The word is photo-reference.