I saw a Ford Pinto that could go backwards - musta been a "3D" Pinto!!!!!!!!!

Luke 3D returns wins the prize. 3D is 'flying' when the wing is stalled, ie, lift is generated from the engine thrust more than the wing.

Think about it - "D" means dimension. Dimensions are both plus and minus, 'forward' and 'backward' -if you must think of it that way- is still the same dimension. Three dimensions was not invented by model helicopter pilots, this concept has been around a long time. "Axis" might be a better descriptive term for flying objects.

Objects moving on the ground are generally thought to move in two dimensions - forward and backward is one, left and right is the other. Objects that fly can also move in the 3rd dimension - Up and Down!