This game's building and flight mechanics are very simple which means its very easy to exploit them. You may want to build a plane that would seem to be aerodynamically sound. WRONG. To a certain point this game cares more about weight than any other factor.

This guide fully relies on using the move tool to force objects inside each other, don't worry, if anything it makes your plane work better. There are no collisions between parts.

Its assumed you will want a fuel efficient plane, In my experience the Wood Engine is best as far as cost, fuel consumption, and thrust. If you want more thrust just add another, don't even bother upgrading to something like the normal engine. The small propeller engine is better but less cost efficient if you spam it, so you do you. The only other engine I used in my career play though was the Prop Fan Engine, since it is more fuel efficient than the Small Jet Engine.

Angling your engine honestly isn't recommended because you may get a shorter take off yes, but the engine becomes extremely fuel hungry. Its more worth it to prop you plane up on two wheels in the front and no wheel in the back.

Paying attention to the amount of lift a wing gives is very important, For example the Delta Wing has 33 strength but only 15 lift, the canard which is much smaller has a strength of 50 and a lift of 10. Very little difference with a huge size difference.

You may expect to need to have a vertical stabilizer or Elevators, uhm.. you dont

Its also worth mentioning you can build a plane with one wing used, yes it wont have much lift but using the move tool to force a wing to be centered does work, just cant recommend it on planes carrying a heavy load or if your expecting stable flight.

Angling you wings also barely changes flight performance. I've notice it might try to fly the direction the wing is facing, or pull to that side, but its still possible.

Most landing gear in this game does not have a drag factor, you can check if it does by checking the planes drag.

Landing gear can be overloaded with weight, yet your plane will handling it better if you have gear on the front and none on the back. Especially since it seems gear being overloaded is calculated by the area, so even if you have strong gear in the front, the weaker back one will break anyway. And there is no damage in dragging your tail.

Its also a good idea to use the move tool and jam a bunch of wheels in the same area, this spreads out the load factor among the wheels. (it barely matters if they are offset because their suspension will still have the aircraft level)

You can fit more cargo into a smaller plane extremely easily. If you have played KSP you have probably stuck a bunch of fuel tanks in one spot to make your plane or rocket smaller, this is the same.^^
Costs 4865. Holds 153 cargo Weight: 28.2

Its worth noting there is a better way of doing this, its less cost efficient but it will give you a much lighter plane which in return less of your lift and thrust needing to be increased. By using the move tool you can jam cockpits inside of each other then into your fuselage. ^^^
Costs: 5734. Holds: 328 cargo Weight: 28.8 (doesnt need the extra engines to take off, thats just what I upgraded it to throughout the career)

Or if you really need cargo
^^^
Costs: 29954. Holds: 861 Weight: 81.2

This editor can be extremely painful, especially when using the move tool and mirror mode. SAVE YOUR BUILD, a mistake which might cost you hours or make you hate yourself for hours.

For example while using mirror mode, I clicked on my wing (made them out of fuselages) and it deleted half of it on the other side. Its scary, so make saves

Its my first guide, I know I ranted a little but I have found this game a calming plane builder so I thought Id share what I have found out. Thanks :)