I have seen this more than once at Potomac Airfield, which I own; a privately-owned public use airport next to Washington DC (
www.potomac-airfield.com).
It may be the principal owner is deceased, lost their medical, does not know what to do with the aircraft, but remains so attached to it they are unable to part with it. Or maybe dealing with other financial medical or personal crisis and don't have the bandwidth to resolve it. Maybe just not using the airplane, they skipped one annual, then another, then another, and now are fearful of what it might cost to take through the next annual, etc. Maybe clouded title, missing logs, etc.
So the airplane sits.
Technically, based on LOCAL codes, anything left abandoned on a commercial property for not very long (defined by local state or county law) is subject to being impounded / sold for outstanding storage. Self-storage places deal with this all the time. Check your local laws.
On the rare occasion this happens at Potomac, I threaten to liquidate for storage, which I can legally do, but also present them some solutions at the same time. That always works, and the owners are always thrilled that I have finally given them incentive AND A SOLUTION or two or three.
If the airport has not been paid for storage, there will be accumulated charges. The airport owner should know who brought it in, who WAS or IS paying for storage, and what that balance may be.
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FIND THE OWNER, IF ANY
You have a few decent civilized paths to pursue. The owner, or lack thereof has a problem, and you can offer some fair and equitable solutions.
I would mail a registered letter to the address of the owner of record and see if it gets delivered, and then see if you get any reply. Save your copies of that action. Maybe some google searching too. If the address is within striking distance, go visit the owners address and knock on the door.
There may be an owner or widow who doesn't have any idea what to do, etc.
DETERMINE OUTSTANDING UNPAID BALANCE
Approach the airport and find out if the storage account is overdue, or who is paying it, or last did, or no longer is, and what that balance may be. There may be a lien filed, or there may not. A lien at least identifies all the related parties.
DETERMINE VALUE
If you CAN track down the owner in distress, there are sort of two ways to value an airplane.
AS IS, WHERE IS
One is, 'as is,' based on what equivalent condition aircraft sell for. Prices of clean aircraft have risen so far that even dogs can be rehabilitated economically. As a result, most dogs have been redone, so the number of bottom-end aircraft has been mostly cleaned out. The good news is that even a dog CAN be rehabbed over time. I have seen aircraft at Potomac I thought would never fly, bought and flown out.
TOP MARKET MINUS COST
Another evaluation is what it would be worth if all straightened out, MINUS (discounted for) whatever needs to be straightened out to get it to that prime condition.
What would it be worth with overhauled or low time engines, complete logs, sexy avionics, 9 or 10 paint and interior, minus the costs of getting it there.
BOTTOM
At the bottom end, you resolve the storage charges with the airport, 'as is' 'wherre is'.
As an airport owner myself I never want to really foreclose for storage, not only for moral and ethical reasons, uncomfortable with taking advantage of someone's distress, but also because setting my own foreclosure price for storage would be somewhat dubious. But that value CAN be defined reasonably for any independent third party to resolve.
Usually, to liquidate for unpaid storage the airport must post a public notice of auction somewhere. That can be a local paper, or online, or whatever. Keep a copy of that public notice.
At this bottom end, to fairly compensate the owner/widow IF they exist, you can even put extra funds in escrow for some reasonable time, based on the condition 'as is,' should the owner ever appear.
LIENHOLDER
The owner may have died and a bank is sitting on an unpaid loan. Do a title search with AOPA, or insured aircraft title and see if any outstanding liens.
Another thing that happens is, aircraft have liens outstanding from banks that are long gone, so getting clear title can be difficult. But there are ways to resolve that too, just more complicated, and to be subtracted from the value of the aircraft 'as is,' 'where is.'
SUMMARY
Identify outstanding balances with airport, as well as who paid last, with airport.
Make every reasonable effort to reach the owner
Determine unknowns - missing logs, condition, liens, etc
Resolve either through owner and resulotion, OR through liquidation for unpaid storage