How to build a working plane?

@Skywylder - I don't know for certain, but I think A380 has an automatic system to pump fuel foward or back to control the CoM (in aeronautics we still often say "center of gravity or c.g.). I'm thinking they have an optimum static stability margin and minimization of trim drag.
https://en.wikipedia.org/wiki/Static_margin

@swope is right, the col should be farther behind the com, the bigger the plane is.

empty most of the fuel. I stayed with the given size, thrust and liftoff mass. Then it should work. And landing gear. Lots of landing gear

Tag me, I’ll make it fly

Start with something simpler.

Here's a fighter I did: https://youtu.be/8d-WLo_piSo

Keep a close eye on center of mass, center of lift, and center of thrust. CoL should be just a little behind CoM.