It was bigger than most 'Park Flyer' R/C planes and flew relatively low over my neighborhood. It traveled at a FAST speed and was completely silent (no normal electric motor noise, zero prop noise.. etc). Both my wife and I said "Did you see that?!?" the first time it passed... and then a few seconds later it flew back from the opposite direction and was gone (again.. it was moving at a crazy speed for being so low).

My house is on the South/West bench of Herriman (Utah.. in the Rosecrest neighborhood), right up next to the hills that back onto Camp Williams (up by Blackridge Reservoir and my deck faces Secret Canyon Trailhead and South Mountain).

My wife thinks it was a military fixed-wing UAV from Camp Williams.
I think some neighbor got themselves a new FPV R/C toy... but for how big and silent it was it seems reckless to fly that low over a neighborhood.

So maybe my wife was right.

Does anybody know if they do any UAV/Drone training at Camp Williams?