....An April 2001 collision between a U.S. Navy EP-3E signals intelligence aircraft and a Chinese fighter revived interest in a high-altitude, long-endurance UAV. Various designs were considered, including a V-tailed Lockheed Martin concept called Distant Star (or Penetrating High Altitude Endurance), but great things were expected (at the time) from high-resolution, space-based radar. Consequently, expectations were scaled back, and in late 2001 or early 2002 Lockheed Martin was awarded a contract for a simpler, medium-altitude tactical stealth UAV, which became the RQ-170 Sentinel.....
....Also in 2006, the Quadrennial Defense Review terminated J-UCAS. It was openly reported at the time that while the Navy continued with its carrier-based demonstrator (the Northrop Grumman X-47B), Air Force J-UCAS money was going to a classified program. At the time, the RQ-170 was just starting flight tests, and two batches—totaling fewer than 20 aircraft—were ordered. It would serve as a stopgap until the bigger aircraft was ready.....