An $86m Drug Enforcement Administration plane purchased seven years ago to fly surveillance and counter-narcotics missions in Afghanistan remains grounded in the US and will probably never fly in Asia, according to a scathing audit released on Wednesday by the Justice Department’s inspector general.

The review, which was spurred by a July 2014 whistleblower’s report, found that the Global Discovery program to modify the ATR 42-500 aircraft to provide the DEA with advanced surveillance capabilities was supposed to be completed in December 2012. But it has been plagued by missteps costing the agencies $86m, or four times the initial estimated cost. The project was part of an agreement with the Defense Department.

The report said it was unlikely the plane will ever fly in Afghanistan because the DEA has ceased aviation operations there.

“Our findings raise serious questions as to whether the DEA was able to meet the operational needs for which its presence was requested in Afghanistan,” the review said.

The DEA said in a statement that it agreed it “can and should provide better oversight of its operational funding” and was reviewing its policies and procedures.

The drug agency spent $8.5m on parts for the plane, “the majority of which cannot be used on any other aircraft in its fleet”, and the Defense Department built a $2m hangar in Afghanistan for the plane that was never used and probably never will be, the report said.

The plane, which has missed every scheduled delivery date, is now estimated to be completed in June – nearly one year after the DEA pulled out of Afghanistan. The report said the DEA intends to fly the plane in the Caribbean, Central America and South America.