A successor to the storied U-2 spy plane is reportedly in development

Lockheed Martin is developing a successor to the storied U-2 spy plane, Flightglobal reports.

Lockeed Martin's "Skunk Works," the office in charge of developing the company's high-end future defense systems, is in the planning stages for a spy plane that combines the best features of both Lockheed's U-2 and Northrop Grumman's RQ-4 Global Hawk drone.

The RQ-4 and the U-2 already perform similar operational roles. But the Global Hawk is more difficult to detect than a U-2 and is unmanned.

Ideally, Skunk Works would combine the best features of the Global Hawk with the U-2 to create an optionally-manned high-altitude surveillance aircraft with the latest sensors.

The U-2 is a high-altitude manned surveillance plane. With a service ceiling of up to nearly 85,000 feet, the plane is capable of flying for 8 hours at a time at speeds of 500 miles per hour.

The RQ-4 is also a high-altitude surveillance craft, although it is unmanned and flown by a team of remote operators. It was originally designed to complement manned surveillance craft such as the U-2, although US military planners have long intended to replace the U-2 with the Global Hawk.

The Air Force has determined that its U-2s can be kept capable of flying until 2045. But due to a shrinking budget, the U-2 is slated to be retired by 2019. This looming deadline has prompted Lockheed to try to develop an updated version of its iconic spy plane.

"Think of a low-observable U-2," Lockheed's U-2 strategic development manager, Scott Winstead, told Flightglobal. "It's pretty much where the U-2 is today, but add a low-observable body and more endurance."

By being optionally manned, Lockheed hopes that the U-2 successor could offer a wider mission range than either a solely manned or unmanned aircraft, Winstead told Flightglobal.

Alongside the B-52, the U-2 is the longest serving aircraft in the US Air Force. Both planes were introduced in 1955 and have been in the US fleet ever since.

Because of the plane's ability to operate at extremely high altitudes, the Air Force maintains that the U-2 is one of the most effective reconnaissance platforms ever built. The U-2 is generally cheaper to operate than surveillance drones, and it has become a staple aircraft in the monitoring of the Korean Demilitarized Zone.