A new DARPA aircraft designed by Aurora Flight Sciences to experiment with active flow control technology has been designated the X-65, elevating the program’s status and indirectly revealing the existence of two other X-planes.

DARPA announced the new designation for the 7,000-lb.-class uncrewed aircraft system (UAS) in development with the Control of Revolutionary Aircraft with Novel Effectors (CRANE) program, which seeks to prove how to control an aircraft without using moving surfaces that increase its profile to radar.

The naming of the X-65, however, comes two years after the Air Force Test Pilot School redesignated the F-16 Variable In-Flight Stability Test Aircraft as the X-62.

But the Defense Department has made no other announcements about designation assignments for the X-63 and X-64. It is possible the designations belong to other known experimental aircraft projects, such as DARPA’s Liberty Lifter or the Speed and Runway Independent Technologies (Sprint) programs. Historically, some designations get assigned to projects that are canceled before an aircraft is built.

Aurora’s X-65 is scheduled to begin flight test in 2025, sporting an unconventional joined-wing configuration that resembles a nearly 30-year-old McDonnell Douglas UAS concept called SensorCraft. McDonnell in 1997 merged with Boeing, which acquired Aurora 20 years later.

Concept renderings have depicted the X-65 with 14 active flow control arrays placed across the coplanar joined wing and twin tails.