"Joint Unmanned Combat Air Systems" (J-UCAS) refers to a research and development program initiated by the United States Department of Defense (DoD) in the early 2000s. The program aimed to develop and demonstrate the capabilities of unmanned combat air vehicles (UCAVs) that could perform a variety of military missions, including reconnaissance, surveillance, and strike operations.

The J-UCAS program was a joint effort between the U.S. Air Force, Navy, and Defense Advanced Research Projects Agency (DARPA) to explore the potential of unmanned systems in combat operations. The program focused on developing two primary UCAV systems:

1. X-45: Developed by Boeing, the X-45 was a prototype UCAV designed to demonstrate the feasibility of an unmanned system for strike missions.
2. X-47: Developed by Northrop Grumman, the X-47 was another UCAV prototype designed to demonstrate the capabilities of an unmanned system for reconnaissance, surveillance, and strike missions.

The J-UCAS program aimed to achieve several key objectives:

• Develop and demonstrate the ability of UCAVs to perform combat missions autonomously
• Integrate UCAVs with existing command and control systems
• Explore the potential of UCAVs for reconnaissance, surveillance, and strike operations
• Develop and demonstrate the capabilities of UCAVs to operate in a network-centric environment

Although the J-UCAS program was canceled in 2006, it laid the foundation for the development of future unmanned systems, such as the U.S. Navy's Unmanned Combat Air System Demonstration (UCAS-D) program, which led to the development of the X-47B and the MQ-25 Stingray. The J-UCAS program also contributed to the advancement of autonomous systems, sensor technology, and network-centric warfare capabilities.