Since World War II thousands of retired warplanes have been stripped of their weapons, engines and most electronics and donated for use as displays in museums or public spaces. This used be rather cheap, compared to retired warships. But that is changing as the first stealth aircraft (an F-117) was prepared for use as a museum display. That was because most stealth aircraft incorporate expensive, and toxic, paint and other materials to obtain their ability to defeat detection by radar. Removing these materials is necessary because of security concerns. The composition of the materials and paints still contains information you want to keep secret. So it cost several million dollars to “scrub” the F-117 so it could be safely (in terms of health and national security) displayed in a museum.
The situation is worse for ships, in large part because of rust and now the removal of nuclear power plants. Starting in the 19th century it became increasingly popular, especially in the United States, for the military to donate retired ships, and then vehicles and aircraft to local governments for display. The “museum ships” became particularly popular after World War II. Most of these were smaller ships, like PT Boats, patrol boats or landing craft. A small seaside town could afford to maintain these small craft with local volunteers and some cash donations. But many cities sought to obtain large ships. The big problem, for whoever takes the ship, is money. Lots of money. Hundreds of millions to outfit the ship as a museum and maintain it.
The navy has long been willing to donate old ships to groups that were willing to maintain the retired vessels as museum ships. But the navy attaches some very expensive strings. That is, the navy expects the ship to be kept in decent shape. This is a problem with many old metal ships, as they rust. And eventually they rust so much that the hull is breached, and ultimately will collapse.
For example, one museum ship, the World War II Essex class carrier USS Intrepid in New York City, returned to its display berth in 2009 after a two year refurbishment costing $120 million. The entire hull was examined, in dry dock, for decay, and over a hundred square meters (nearly a thousand square feet) of hull had to be replaced.
Current nuclear powered carriers are a lot more expensive. Not only are they larger ships but you now have costs of over half a billion dollars to retire a nuclear powered carrier. Most of that goes to removing and disposing of the nuclear reactors. That leaves the carrier partially disassembled and in no shape to be a museum. In contrast a non-nuclear powered carrier costs less than $60 million to decommission. The first nuclear powered carrier (the 93,000 ton USS Enterprise), which began the decommissioning process in late 2012 (with the lengthy removal of all classified or reusable equipment). The cost of dismantling this ship (and disposing of radioactive components) may be close to $2 billion.