The Air Force has reduced the operation and maintenance costs of the Global Hawk drone in recent months, an official said, as the spy plane faces increased scrutiny for its high costs and questions about its effectiveness.

Lt. Col. Ricky Thomas, the Air Force functional manager of the RQ-4, said the operations and maintenance costs have been reduced by 5 to 10 percent since June 14 as the service scrubbed the program to look for savings and phase out inefficiencies.

The June deadline was imposed under the Nunn-McCurdy statute, which allows Congress to terminate a program that exceeds a 25 percent cost-increase threshold unless the Pentagon certifies it’s vital to national security.

“Costs are coming down,” Thomas told reporters at the National Press Club in Washington on Wednesday.

Global Hawk is a high-altitude unmanned aircraft designed to conduct intelligence, surveillance and reconnaissance and is built by Northrop Grumman [NOC]. Among the aircraft’s customers are the Air Force, Navy, NASA and foreign governments.

Thomas said the Air Force plans to replace its aging fleet of U-2s with Global Hawk by the end of fiscal 2015. But lawmakers have insisted that the RQ-4 demonstrate it’s an adequate replacement for the U-2 and will not result in an intelligence gathering gap before the manned U-2s can be mothballed.

The legendary U-2 spy aircraft has been around since the 1950s, and was designed to fly at high altitudes over the Soviet Union.

The Pentagon notified Congress in April that Global Hawk’s cost had risen beyond its 25 percent baseline, largely attributing the growth to a lower-than-expected buy quantity planned for fiscal 2012 (Defense Daily, April 14, 2011).

The increase triggered a mandatory review under Nunn-McCurdy. The Pentagon later certified the necessity of the program, spokeswoman Cheryl Irwin said.

Further complicating matters for Global Hawk was a report by the Pentagon’s top tester, Michael Gilmore, that found the newest version of the plane–designated the RQ-4B–could not effectively conduct the type of persistent spying for which it was intended (Defense Daily, June 7, 2011).

The report stated that during a seven-day “mission surge” demonstration, the Global Hawk delivered 39 percent of requested intelligence, surveillance and reconnaissance (ISR), when low operational tempos of up to three sorties a week with three aircraft were used.

The Operational Test and Evaluation report said a combat patrol of three air vehicles and supporting ground stations failed to “consistently generate or sustain long endurance missions to support persistent ISR operations.” When operating at high operational tempos, the system provided less than half the required 55 percent Effective-Time-On-Station coverage over a 30-day period.

Thomas, however, said the Air Force has begun to address the deficiencies and he was confident Global Hawk will be ready to replace the U-2 by 2015.

“We’ve made really great strides,” he said.