* For a moment, let's ignore how hypocritical and childish Koko's ideals are here. Or that activating this system would kill more lives than it would save. Or that the moment other countries found out about it, it and Koko would become the biggest target in the world (and even she can't take on the entirety of mankind). My question is: how could the Jormungand System possibly assure world peace simply by removing air travel? And even if that weren't the only thing it did, how could it stop humans from being a race that fights itself? Even if she put mankind into the stone age, they'd just use sharp stones and their bare hands.
** Kaspar makes the exact same points to Koko in the final episode.
*** The BIGGER head scratcher is how Jormungand could possibly work as advertised (cut mankind off from air travel). Even IF it has the ability to hack modern aircraft using digital communications and GPS navigation...how would it hack an airplane that didn't have a computer on it? Or a plane that had a computer that didn't have a connection to the network Jormungand was on? If a plane has no inputs to receive the hack commands to crash, how will Jormungand make the aircraft crash? Magic? It's not like you're even limiting aircraft's offensive weaponry that much. The laws of physics are still the same, so missiles and bombs can still be guided based on heat, radar, or laser guidance. Did Koko kill 700,000 people to deny the world the right to GPS guided weapons?
*** Note that it's also not explained how in hell it's supposed to prevent missile warfare (up to, and including [=ICBMs=]). Missiles were born quite before GPS, the latter just gave some of them a terrifying accuracy. I got a feeling that the story originally included a subplot about ''hooking'' world's military on to some global information carrier, and only ''then'' going with the "hack them all" plan - but for some obscure reason the author decided to drop out that subplot completely.
*** But wait, there's more! The US, Russia, and China have all demonstrated the ability to shoot down satellites in orbit. There's no particular reason that Jormungand can't just be dismantled. Even if it's left in place, there's no reason to believe that it's going to be effective for much. Now that everyone knows that wireless communication is insecure, the armed forces of the world will probably just revert technologically a bit. We didn't have the internet or GPS back in the 1940's, and that didn't do much to slow down World War II. In the best case scenario, all Koko has really accomplished is to revitalize the postal service. More likely, she kicked off World War III.
*** Answers to almost all those questions are easy enough, assuming that by hacking and controlling the information and logistics involved, one could easily misdirect anything in the air to someplace it really shouldn't go. Like what she did with the Night Nine, by feeding them a false map. With airplanes, flights longer than to your own private field and back require logistical ground support to direct them to their intended location, as well as to help with issues like extreme weather patterns. For missiles, yes, in flight, there are plenty of missiles that go to a broad, inexact location, but to launch one accurately, one must have some kind of map one could put coordinates into for the missile to go to. They don't magically know where to go, after all. And finally, the reason they CAN'T take Jormungand out of the sky is simple: It's close to impossible to tell which satellites are which from the ground, and it wouldn't be too hard to keep all information pertaining to Jormungand to a very limited few. Even if you could find out about it, and tell which one it is consistently, you can't launch a missile at it without a lot of work. Which can't be done because all the information is controlled.
*** That still doesn't ensure world peace at all. All she did was keep fighting restricted to sea and land which is coincidentally quite beneficial to an arms dealer. Now, instead of accurate missiles being used to fight, inaccurate missiles are gonna be used to fight and will probably cause a lot of collateral damage. Koko's plan is highly implausible (well she is insane) and if anything was to go wrong with Jormungand, she might not be able to do anything about it being the world's number 1 target for killing hundreds of thousands of people and such...
*** Given that Koko's plan has a large amount of collateral damage ''built into it'', and is so vaguely-outlined that you really could believe it came from the mind of a lunatic... Essentially, the entire series points to Koko being a zealot/fanatic, convinced that her plan will bring about world peace. If she believes that, she'd probably see any fallout as being worth the risk, since it's unlikely she'd consider the failure of her plan. That said, the "answers" given above are a ''huge'' assumption: It assumes, among many other things, that her control over information is absolute, and will ''stay'' absolute, even after her death. If it weren't for the fact that Koko is a BoringInvincibleHero, and is surrounded by the same, it's likely that someone would find a low-tech way to kill her and/or disable Jormungand soon enough, especially since she's just united a world against her. Not to mention the fact that, if all the world's information is ''already'' in the hands of someone who's killed hundreds of thousands of people and may choose to do the same at any time, the various nations might not be so concerned about the fallout of accidentally shooting down the wrong satellite when not even trying could have even worse consequences. Given Koko's actions, would anyone actually believe her if she said "Oh no, I just want peace!"
*** For the information control part people seem to forget the sat network put in place for the worlds military and presumably everyone else to use for any logistical use, and Koko just happened to build Jormungand into that network. Also it would not matter if Koko was killed because once the system was activated killing her would not stop it from still running. As for a "low tech" way of taking out a satellite well good luck with that, not sure there is any "low tech" way of blowing up something orbiting a minimum of 93 miles (min altitude for an orbital sat) in the sky.
*** Satellites require maintenance, unless Jormungand is infinitely self-repairing. Either we're assuming the world will fold before any maintenance needs to be done or Koko's going to need some way to get up to Jormungand (not necessarily in person) and perform upkeep, which could easily be exploited by destroying said transport and waiting for Jormungand to fail. Killing Koko may not cause the satellite to fall but will almost certainly be a priority for the countries and powers affected by Jormungand, if only because getting rid of her will allow the world to find a way around Jormungand/an alternative to previously-compromised systems without having to worry about Koko and crew taking countermeasures. As was pointed out by another troper above, [=ICBM=]s are still viable means of destruction as they don't have to be particularly accurate to be devastating, especially in large numbers.
* Why the heck does anyone believe Koko for a second that she wants world peace, when she shows time and again that she's a megalomaniac and possibly insane person who just wants power? Not to mention world peace would essentially drive her business down to nil. It honestly comes off like she's just flat out lying to everyone and just sees the entire thing as a way for her to get even more power.
** Who knows that she may have her own way of ensuring world peace.
*** Why would it matter if her business of arms trading goes away? Given she was able to sink the funds into creating Jormungand I think it is safe to say she is one of the richest people in the world.
* Why, with a clear shot at both Orchestra assassins, did a veteran soldier who had a suppressed weapon and demonstrated accuracy with it, not kill them both? Lehm was standing BEHIND both, and instead stands around calling in heavier weapons and directing team members to better positions. The entire episode 3 gunfight made me groan aloud.
** I thought that Chinatsu was able to "sense" Lehm's incoming shots when he attempted to shoot Maestro.