I would like to add suggestion to separate A330 and A340 production.
While both Aircraft share lots of common components such as cockpit, or interior style. But then again they have lots of difference as well, such as engines number, or fuselage length, or engine type, and the new generation A340 (-500/-600) have different wing size.
Now many people would argue that A330 and A340 are just like B777 family, they have different fuselage and different wingspan, as well as different length. Why would we separate A330 and A340?
1. Well logically speaking, they are from 2 different family of aircraft, hence why Airbus Called them A330 and A340 instead of A330-400 or A330-500.
2. The number of engines used on an Aircraft play a big role for the overall design of the aircraft, to be honest it would be one of the main key that determine an aircraft type and final performance. Just like B747 and B777.
3. The 2 aircraft are intended for different market, just like B757 and B767.
4. They have quite different design with the wings especially with the new generation A340 (-500/-600 series)
5. And the maximum fuel capacity are quite different with one of another which would affect the Maximum weight to operate between the A330 and A340.
6. Also A340 have extra landing gear in the middle of the fuselage to withstand the more weight the plane carries.
7. With A330NEO coming up in just 2 years. I think it would be more appropriate to categorized A330 and A330NEO in the same family aircraft compared to combining A330 and A340 at the same family.
I know both plane look and have lots of similar components. But it's not close enough to be classified as 1 family type.
Now some say that A330 and A340 could be categorized as A300 and A310. Well it's not true because A300 and A310 shared more common characteristics such as engine quantity, and same structure, it basically a same plane with different fuselage length and different engine type.