In August 2015, the 60th-year anniversary of the U-2 program, Lockheed Martin's Skunk Works revealed they were internally developing a successor to the U-2, referred to as the UQ-2 or RQ-X, combining features from both the manned U-2 and unmanned Northrop Grumman RQ-4 Global Hawk and improving upon them. Disclosed details say the design is essentially an improved U-2 airframe with the same engine, service ceiling, sensors, and cockpit, with the main differences being an optional manning capability (something Lockheed has proposed for the U-2 to the Air Force several times but has never gained traction) and low-observable characteristics. The Air Force has no requirement or timeframe for a next-generation High-Altitude Long Endurance (HALE) platform, but Lockheed sees a future need and wants something in development early. Having the option of an onboard pilot is considered a deterrent because it can be used in peacetime situations where unmanned aircraft would more likely be engaged, since there is no possibility of killing a person. The company's last attempt to create a stealth unmanned aircraft was the RQ-3 DarkStar , which never made it past flight testing and was canceled.  Plans for a U-2 replacement would not conflict with development of the SR-72 , another project by the company to create a hypersonic unmanned surveillance plane, as it would be suited for missions that require greater speed for time-sensitive targets.