The Airliners Magazine, November/December 2002 (issue 78), had an article on how the airliner scrapping process takes place. Taking from other articles of other sources in addition, I'll try to put this into a "scenario" format.
Lets say YX
retires all of their DC-9's (which they did). The airplanes are often bought by a company that sells used parts. From here, the planes are ferried to hell (aka Opa Locka, Marana, etc), where they are immediately parted out. Any part that can be resold is pulled off the airframe, and stored in that company's warehouse. The parts are put on shipping crates and protected with "packing plastic," where they wait until a buyer in need of parts purchases them (lets say NW
, since the operate alot of DC-9's). Then the part is barcoded so that it's life is traceable, and shipped out. Meanwhile, when just about all of the usuable parts have been removed from the airframe, the airframe is torn apart by machinery, and the subsequent "scrap metal" is recycled.
However, this scenario is a very quick method. Often times, retired airplanes are stored, waiting for a potential buyer. If no buyer is found within a certain period of time, that airplane is unfortunately scrapped.
Sometimes, it takes even decades from an airplane's last flight to its last recognition. Again, my scenario was a quick one, based on an actual scenario in the Airliners Magazine involving an ex-Canadian B-737-200 (C-GAPW).
Anyways, I hope this helps