Aircraft serial number
 

Which part of the aircraft does the serial number actually apply to?
As you keep changing components over an aircraft's life, including possibly wings and parts of the airframe, at what point does the manufacturer's serial number become no longer valid?
Or even, if I cut my aircraft in half, and rebuilt each half with spares, where does the serial number go? Does it still apply to both halves? It only to one half, what serial does the other get??????

Every component replacement / exchange / repair is considered a repair of the original aircraft. The original aircraft, and this is to be seen as the fuselage, will maintain the SN until scrapped as a total.
During the scrapping individual parts may be selected to gain a second or even third live on another aircraft. The said part will be identified in the documents as a part coming from the original aircraft.

This has been, in certain circumstances, a major issue in the past as crashed or wrecked aircraft parts have been illegally (no valid labeling) sold and subsequently fitted to aircraft.

Documentation is a challenging job, not easy and it needs a great understanding of the system.