The US Drug Enforcement Administration (DEA) spent $86m (£60m) on a spy plane to be flown in Afghanistan, but it was never used, a government report says.
The plane, to help fight the Afghan drug trade, cost a tenth of that sum and millions more went on upgrades.
But to this day, it remains in storage in the US state of Delaware, a report by the Inspector General's Office of the US Justice Department says.
It adds that the plane is unlikely to ever fly in Afghanistan.
The programme for which the plane was bought ended in 2015.
The ATR 42-500 plane was to be used in an anti-drug programme led by the DEA and the Pentagon, but costs to modify and house the aircraft quickly escalated.
Some $67.9m in funds from the US Department of Defence were spent on the plane and on a purpose-built hangar in Kabul, four times more than the original estimated cost.
The report says aviation officials with the DEA "did not take into account, when purchasing the ATR 500, the time and cost it would incur to establish an infrastructure of pilots, mechanics, trainers and spare parts required to operate the aircraft".
It adds that even though the plane was bought more than seven years ago, it "remains inoperable, resting on jacks, and has never actually flown in Afghanistan".
A DEA official told investigators the plane, once ready, would fly in the Caribbean and Latin America, but the report notes "that was not, of course, the purpose of the funding".
Goats 'may have been eaten'
The revelations come two months after a US government watchdog accused a Pentagon agency of wasting millions on "ill-conceived" reconstruction projects in Afghanistan.
Special Inspector General for Afghan Reconstruction John Sopko noted one programme that spent $6m to import rare blond Italian goats to help the Afghan cashmere industry.
Oversight was so ineffective, Mr Spoko said, he could not be sure that the goats were not eaten.
Last year, Mr Sopko said some $43m was spent on building a vehicle refuelling station in Afghanistan, 140 times the cost of an equivalent station in Pakistan. He said fraud and corruption may have increased the cost.
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