A Line of Drones Monitoring the West Cascade Ridge?

I saw a series of what, at first, could only be discribed as a line of bright stars. Located between Mt. Hood to Mt.Jefferson these "stars" were in fact moving. Ever so slowly, they could be seen cruising at an altitude of aprox. 5000 ft. They had 4 small lights that would suggest a standard aircraft shape. A hum , very low frequency, was barely detectible in their presence.
My thoughts, people will run to the mountains in the event of an emergency. Perhaps these slow moving vehicles will report to a higher source that the boundaries have been breached.
The technology of these vehicals is quite impressive because (a) they are extremely quiet. (b) they are extremely slow and hard to spot w/o binoculars. And (c) they seem well controlled and at an altitude just beyond a conventional rifle's range to engage them.
Bike Paths for armed invasive ground-based drones are nothing new, but an invisible wall across a mountain range is disquieting in so many ways.
Agenda 21? Weird.