Well, that was a very long read indeed! Look, I normally try give only positive feedback in these kinds of threads, but considering that applying my "normal" ranking standards to your factbook would just produce a 10/10 and not much more to say, I'll take the liberty to be picky and pedantic. I think you will also find my honest opinion about this factbook way more useful than a watered-down opinion, considering the great amount of effort this factbook seems to have received, and how passionate you seem to be about this stuff.
I'll start with the positive stuff. The general structure of the factbook is extremely well done and professional-looking. The writing style is very clear and uses very serious and realistic language that makes the whole thing feel very real. I'm sure you can make the average person believe this thing is actually real. Heck, if you replaced the name of your nation with the name of a real one and publish this on another web that is not NationStates, I would believe it too! I also appreciate that the factbook is very organised, with clear sections and subtitles, and a lot of links to external pages that contribute to the general feeling of this being real. I can't even imagine how much time finding and compiling those pages must have taken. On a side note, I also have to commend you for your formatting. While it is still rather simple, it looks very clean, and the images you chose to use in the factbook are very beautiful and eye-catching. The fact that you also credited the authors of said images is also something very commendable. To be honest, this whole thing truly shows that you are passionate about the stuff you write about.
Moving on to the not-so-positive stuff (and please keep in mind this all comes from my pedantic and picky self, I still think the factbook is top-quality)... I'll start by directly addressing the elephant in the room. The factbook is simply way too long. I know this may sound a bit hypocritical coming from a guy who also has horribly long factbooks, but regardless of that, I think it is important I address this, as I think this is also something my own factbooks suffer from. When I opened your factbook and saw its extent, I doubted if I wanted to read it or not just because of how long it was. That feeling was worsened by the fact that your factbook is about a very niche topic. Let's be honest here, the number of people who are interested in learning about the planes of a nation is probably not very big, and if you combine that with a very long and detailed description, you get the perfect combination for people to simply ignore the factbook.
Furthermore, I must also say that I am not someone who knows much about planes in general, and you use some jargon that may be a bit complex for us (as in, people who are not into planes) to understand. Just to give you an example of what I am trying to say, looking at your "Radar and Sensors" section, I have no clue what a "EL/M-2052 Active Electronically Scanned Array Radar" is. I think that you correctly guessed most people would not know what that is, so in the next paragraphs, you describe it. However, you use phrases like "X-Band Fire Control Radar," "Synthetic-Aperture Radar," "Real Beam Map," "Doppler Beam Sharpening," "Inverse Synthetic-Aperture Radar," "pulse doppler," "monopulse guard channel," etc, etc... I have no clue what those are, and I am bold enough to say most people here don't know what those are either. When I read those paragraphs, I effectively learned nothing about your plane, not because I didn't want to, but because I genuinely do not know what I am reading. Those are just fancy words for me, without much meaning. If you asked me what I thought about the radars and sensors in your plane, I honestly couldn't say anything more than "it has advanced technology that sounds cool" which I guess was not your intention.
When sharing scientific information, or basically anything that requires the reader to have some kind of previous knowledge, I think it is important to place ourselves in the shoes of our intended audience and try not to include jargon that only someone who knows about the stuff you are talking about would understand, and if that is not possible (or we choose to include it anyways) always make sure to add a description or explanation. I know it is hard not to do this, especially because some things can be obvious to the person who writes them, but it is probably one of the most important things if you want to connect with whoever reads what you are saying.
To put it in simple words, it does not matter how great or detailed something is if you direct it to the wrong audience, and I am not sure if the average NationStates player is the most adequate audience for this kind of factbook. I think your work would be much more appreciated in a community that is more into this kind of stuff, and I am sure it would probably be considered a very valuable contribution there.
I'll say this again just for good measure. Your factbook is truly amazing, and I do not want you to think otherwise. I'm being this pedantic just because I think you deserve my honest opinion, and not just a shorter version of this message where I basically stop at what I said in my second paragraph.