Someone that I have known for decades told me a few years ago that they were part of a small group that had an experience with something similar to what you are describing. In their case the thing they all described blocked out the stars almost from horizon to horizon as it passed over. It was described as huge, black, and silent with a well-defined edge that one could follow across the sky as the stars in front were blocked and those behind reappeared. They said they didn't notice it until they realized all the normal night sounds had completely stopped as it approached and once it passed, the insects, birds and things resumed their chatter. They don't know what they saw but they do know they did see something unusual. These are college educated people enjoying life in a rural area.
While in college, I also taped a story that a fellow student told one day. I always taped the lectures and transcribed them after class to help remember things and on this particular day the subject somehow turned to UFOs. I would have to replay the tape to know how the segue happened but anyway, if I remember right the professor commented about UFOs not being real and this student interrupted a told his personal encounter story. From memory, he was out with friends riding ranch roads across the part of west Texas where he was raised when one of them pointed out a set of lights over a part of the ranch where there were no roads, buildings, etc. They all saw the lights and decided to investigate and so they followed ranch roads towards them and as they got closer it was apparent that the lights were part of something really unusual and large that was not on the ground but was in the sky. As they got closer it zipped straight up and away and was gone in a couple seconds. I still have the tape but no way to play it. I always recorded over the previous day's lecture after transcribing but for that one I decided I would keep it and start another tape. I know this person to be an ordinary person who got a great education in geoscience and took that into a career with a multinational company eventually as a VP. He was always a no bullshit person.
Sounds like ... a cloud? Combined with some kind of local changes in temperature/pressure/ionization sufficient to distract the animals for a bit? (I live partially in nature - sometimes the critters are very active; other times, one can hear a pin drop).
I acknowledge that a cloud would block the view of everything behind it but in this case I'm pretty sure it wasn't a cloud.
As I'm sure they've been told already. I'm not denying their perceptions; and of course I wasn't there. It's just that my threshold of proof for extraterrestrial vehicles is ... quite high.
And sometimes unexplained observations are just that -- unexplained.
I left out some of the details on purpose since the whole story is not mine to tell. They told me because they knew that I had done a lot of reading about the subject when other friends had something odd happen to them and they hoped that my physics studies would help them understand some of it better.
Some things are just unexplainable with our conventional knowledge. Over time that should/could change. If we already knew everything there would be no more need for science as curiosity about unfamiliar things could be satisfied by a simple query of existing knowledge. It would be a boring reality with no novelty or mysteries. In the worst case, a small group of people would control access to knowledge, withholding key information that would empower the rest of the people by helping them understand how all the mysteries of the world fit together to form our boring reality where every question has a clear, unique answer. Luckily we are nowhere near that point and there are many things left to be discovered.
This is certainly true for the people that I know. With the exception of the fellow student who felt compelled to tell his story, almost every one of the others that I know avoids talking about it and will even try to deflect conversation if there is anyone who hasn't already heard about it present.
One old friend still regularly communicates with me as I am one of the only people they trust to be non-judgemental since I knew them a long time before they had their experience. I get photos, short videos, descriptions of events, attempts to tie their experiences in with other reports, etc and so I dutifully check it all out to try to help them come to terms with what has become for them a lifelong process of dealing with an emotional trauma that ended up stigmatizing them back in the small town where we grew up. Long-term friendships are critical for helping people manage some of these experiences.
Events like this are relatively rare and so it is easy for someone who doesn't personally know or who has never personally had an unusual event happen to automatically default to the conclusion that the one reporting the event has some mental issue, is unreliable, etc. Another poster suggested that somehow the subjects of one thing I mentioned must have been confused by clouds. People look for the most likely explanations and tend to ignore the fact that many of these observers have more than enough experience to understand when they are seeing something remarkable. I can say that I know several people who have had strange things happen in their lives and that among that group there is not a single one who actively went out looking for that to happen. All were just ordinary people and some were still in grade school. I am open-minded about what has happened to these people and in some cases I saw the immediate changes in their personality and demeanor. Something different happened to them. I am not qualified to say what it was but I know it was not something that anyone would consider normal. I'm just trying to be a friend to them - a sounding board when they find themselves thinking about it again.
I personally could buy the "autonomous alien probe sent 10,000 years ago" narrative, but just seems like we'd have more concrete, widely distributed evidence by now.
The size of the one I saw was large and it was already extraordinary and alarming. A formation would be astounding.
I never reported it or anything, mostly due to not knowing who to call and lack of evidence (cell phone cameras were primitive at the time and it was too dark). We still talk about it occasionally, not really knowing what to make of it.