Eric Weinstein has several great threads about this, but I'll summarize some of his points. The military itself is saying it's aliens without using the word alien. It doesn't matter how you read this story, it should be the biggest thing. If there's aliens, it's the biggest story in history. If the military is pulling the wool over our eyes in a psy-op, it's a really big story. If we've been significantly outclassed by a foreign military tech, that's a huge story. But we're not talking about it like this. If it's aliens or enemy military, why are we not collecting our greatest scientists/physicists to work on this?
None of it makes sense no matter which narrative you think is most likely.
My gut reaction is that most folks are brushing it off as a non-event because it doesn't directly concern them, and they've become numb to outlandish, world-changing news.
Kyle Hill makes a very thorough and compelling case for jet engine exhaust in IR, here: https://youtu.be/I_n1xpKBBcs?t=1074
[citation needed]
https://www.scientificamerican.com/article/experts-weigh-in-...
IMHO, the ET solution is both the most boring and the least unsettling. If there is a terrestrial explanation for this phenomonen then that means there's a foreign adversary decades or more beyond American flight technology. If it's ET, then they haven't hurt us yet, and don't appear to be interested in doing so, and also not interested in sharing tech.