When I am in the outside view and I have turned a little bit the camera (something not mandatory), I just use the mouse wheel to zoom in and out and you can see the result on the video.
That's precisely why in the screenshot I posted, I showed the External camera user interface, which shows zoom level at 0%, which is the same as if you rolled back on the mouse wheel all the way back.
What you are looking at is surely LOD.
Somebody else said something about the glass materials, but in your video it's not affecting just glass, but everything else disappears too.
I think the issue might just be your screen resolution a bit lower than the one on my screenshot, which was 2145x1191, while your screen is 1920x1080.
By reducing the window size to 1920x1080, I can replicate the problem ONLY from 0% to 1% of the Zoom level, as soon as I go to 2% and up, it's all normal so, it seems the small difference in size didn't allowed to see the last two 1/100ths of the whole zoom range, but it could on my system with just a bit more screen size.
Problem is, we must optimize the scenery for a wide range of users, and I fear a setting that would gave back those two 1/100th of the zoom range for 1080p users, would make LOD basically not-existent for 1440p and 4K users
who need it moreNote that, this is NOT just dependent on the screen resolution, but also by "Objects Level of Detail" setting.
Try to run the FSDT Live Update now, I've tweaked it a bit, and with 1080p resolution and Object Level of Detail" at 100, it doesn't disappear at 0% Zoom level anymore.
In any case, I still believe that demanding LOD won't ever show up, even at extremely wide zoom settings, is like defeating LOD's purpose, since by optimizing it for the wide zoom levels, we make it useless when it really matters: on realistic zoom settings used during flight and approach, where fps matters the most.