If these are time travelers, the next question is why they visiting us now. You would assume that if a time traveler had a choice of any time or place to be, he would choose those times and places of special significance. Knowing our near future better than we do, these would perhaps be times and places which the time traveler would appreciate as critical but we would not. This is a little disturbing, no?
I think this a very plausible scenario and one that I think makes the most sense to explain these phenomenon
Thing is it is not just us seeing them now recently... It has been happening all along throughout the history of man and civilization. The historical reference to UFOs is gigantic. They are even found in ancient Christian paintings. There are several ancient accounts of huge past battles between UFOs. So they have been around for a long long time.
I agree the idea of some approaching critical-for-the-future event is very disturbing...But I suppose it can be argued mankind has always lurked there?
Then again, if we are on the cusp of something totally self destructive, and somehow being nudged away from the brink, that’s a hopeful thought...
As far as exposure goes, they might have the same regard for us seeing them as we do the ants on the sidewalk seeing us...They’re simply going about whatever their business is without regard of us, confident in the superiority of their technology...