@voltronic
LockMart, DARPA, and USAF have been back and forth on saying that it does exist, either on paper or in prototype form (scaled down to F-22 size), or it doesn't exist at all.
All of the above is a pretty good indicator that such a project does exist (since at least 2013) but they don't want to share any but the most basic of details.
Some of the extreme speed aircraft seen testing over Texas over the last 5yrs may be related, or could be LockMarts X-59 or some other prototype.