Depends. Some are stored until they are sold or reactivated. Others are stored until they are broken up for parts. As for Aerospace Maintenance and Regeneration Center, there are many reasons that airplanes are stored long term. While many are parted out to maintain the active fleet, others are stored for other reasons. Each branch of the services has a unit that documents that branch's history-some aircraft are designated to be preserved for the historical record or to be loaned to museums, municipalities or military legion posts for display. AMARC stores aircraft for other government customers than the military, including the Smithsonian Institution. Boeing's 367-80 and an early United Airlines 727-100 were residents of AMARC for a while-both stored for the Smithsonian.
"When a man runs on railroads over half of his lifetime he is fit for nothing else-and at times he don't know that."