The US Customs and Border Protection (CBP) agency no longer plans to acquire 14 more medium altitude unmanned air systems and faces stinging new criticisms about the effectiveness of the current fleet of 10 aircraft.

The agency’s fleet – comprised of unarmed land and maritime surveillance versions of the General Atomics Aeronautical Systems Predator B – are so restricted by budget, operational and weather constraints that the aircraft have completed 22% of planned flight hours, according to the report by the Office of Inspector General (IG).

Moreover, an $8 million sensor – the Northrop Grumman vehicle and dismount and exploitation radar (VADER) – is not being used properly, says the IG report. Although VADER has detected thousands of suspected illegal immigrants after they have crossed the border, it is not being used by the CBP for the strategic purpose of tracing their routes back to where they crossed the border.

As a result, the IG recommends that the CBP invest $443 million on more useful purposes than expanding the UAS fleet to 24 aircraft.

“CBP has invested significant funds in a program that has not achieved the expected results, and it cannot demonstrate how much the program has improved border security,” the report states.

The report also says that the CBP has stated it no longer intends to expand the Predator B fleet, although an approved requirement for the additional aircraft still exits.

The IG report catalogues a list of details about the CBP’s UAS operations along the southern land and maritime borders of the USA.

Although the CBP estimates it costs only about $2,500 per flight hour to operate the Predator Bs, the IG report says the actual cost is nearly six times higher after factoring in salaries for pilots and maintainers, depreciation and the cost of maintaining the VADER sensor.

The Predator B fleet faces several weather-related restrictions. The CBP does not allow the UAS to operate in stormy weather or where there is cloud cover, the IG report says.

The CBP partly justified the expense of standing up the UAS fleet – estimated by the IG at roughly $360 million – by promising cost savings. The Predator Bs could be used to respond to ground motion alerts along the border, rather than sending aircraft or patrol officers to the source of the detection. But the IG found only six instances where a Predator B responded to a ground motion alert.