As a result of the different production sites of Airbus (e.g. Hamburg and Toulouse), Airbus has always used transport planes to transport parts like segments of the fuselage or wings from one place to the other. In former times this was the task of the Super-Guppies, modified Boeing 377 Stratocruisers. But as time went by there had to be a successor, and so Airbus developed a new transport model out of an A300.
The nickname "Beluga" has the A300-600ST as it looks similar to a Beluga whale. For the Beluga the upper part of the fuselage was removed, and a new, wider fuselage was put on it, which is the cargo section. That makes possible the giant diameter of the fuselage of 7,4m. To enable the big nose door for loading, the cockpit area was lowered and the nose gear was modified. The cockpit is however the same as in the normal A300-600. As a result of the height of the fuselage the tail and the rudder had to be modified.
The first flight of the Beluga was on September 13th 1994. Altogether five A300-600ST fly for Airbus Industrie. Boeing offers this model on the transport market, too, but no airline ordered the beluga yet. But the Airbus ones made already lots of special flights, and transported among other things even parts of the international space station ISS.