[faa.gov]

[uavcoach.com]

@FearlessFly Thank you! I'm a little worn out tonight and didn't even think to look.

This law (see below) could explain it - but why at night? Less air traffic maybe - or fairer weather - more volunteers available to practice?

Whoever it is they should let the folks at the PD know - though there's nothing stating they'd need to - certainly the PD are the folks getting the UFO reports first.

I imagine now that this has been made public a military base could be put on notice to go find out who the heck is flying that many craft out there at once. (presuming it isn't the military). Heck it could be a college with a bunch of enthusiasts? Who knows!?

I can imagine the townsfolk have been wondering what the heck they've been viewing - because the pattern wouldn't appear like regular aircraft they've seen at night. That would freak me right out if I saw that. I know it would. Because the pattern wouldn't look recognizable. (It's not a flight pattern I would have ever seen before).

Way to scare the neighbors whoever is doing it!

@RavenCT The newspaper article cited in the OP link mentioned a need for night flights perhaps due to infrared imaging.

@bingst But for which agency? Heck could be Google maps for all they know.