Details
Fuselage smoothness
Speed
Stability
Easy to BUTTER
Control sensitivity

if it looks like it belongs in a museum, i upvote and comment
if it looks decent, i upvote
if it looks bad, give advice
if it looks like complete shit, i post it in a discord server
if its political and breaking the rules, i report it

I look at a build, and think of the processes and techniques that were used to make it. If it’s up to my standards, and if the thumbnail’s aesthetically pleasing, I’ll upvote it.
Also note that I almost never download stuff I upvote because I’m not on the game often, unless it offers me a superb flight experience.

thumbnail :troll:
Edit: I also check the plan views, since there are a lot of planes that look nice in the thumbnails but fall apart completely when you look directly at the front or side. There are also planes with an interior, but their digital instruments are made so messily that a blank screen would be better. I haven't seen people talk about these areas, so I think they are under-appreciated, or maybe I'm nitpicking.

Stability
Functions (activation groups (more=better depends on prefrences) weapons ect.)
Design
And last but not least
Funni