What are the physical laws for upscaling an RC model to 1:1? What are the laws of physics for upscaling an RC model from a smaller to larger scale or even to a full sized 1:1 aircraft? I guess the basic thing may be lift/weight ratio which was nicely described here:


  ... when you scale an airfoil up, the lift it produces increases with
  its area, which grows with the second power of size, but its weight
  increases with volume, which grows with the third power of size.


The above means the lift/weight ratio is worse for bigger vehicles which I guess makes them fly worse (less range, higher fuel consumption).

Are there any more laws to be taken into account for such upscaling? I mean in terms of aerodynamics or power source (battery/fuel) etc. Does the air behave differently with scale? Do different laws apply for different aircraft types (plane, helicopter, quadcopter etc.)?
This is not a full answer: much is mentioned by Michel Touw, but I'd like to correct a common misconception.

The mass growing as the third power of linear dimensions applies only to solid objects. But the airplane is not solid; rather, it's a thin-skinned frame. (Unless it's a solid foam RC model). Therefore, its mass should grow with the area, as the square of length.

However, this is, of course, not quite true. In reality, you need thicker skin, thicker spars, etc., and these elements will get heavier 'properly' with the cube of length - and even more, because they'll need to support themselves as well, with their added mass.

In the end, the mass of airplanes grows between the second and third power, and much closer to second.

Let's take B734 and B772 for example, which differ close to twice in linear size. Their empty weight (roughly 33 and 140 tons, depending on modification) differs by 4.25 times, which is approx. 22.1. MTOW has a similar ratio: 68 vs 300 tons, 22.15.