...and they didn't land. There were lights & blips on radar...jets chased them. Nothing was caught, 'seen' or contacted. I 'think' of lots of incidents, but landing on the lawn is my catch-all phrase for the sort of data that would convince me.
(remember...always remember...'doubt' is not denying.) I WANT to be convinced....I do not want to get into a mindset of 'believing' which would change my approach to 'examining'.

Stuff like this or this might explain a few things, but not many.

And here is a bit of what CAN be done. I SEE the possibilities of getting varied shapes to fly...but getting them across the Universe?

I wouldn't bet against the US building some experimental stuff that gets seen at odd times...but that's not the claim that at issue. What we DO have is many stories, experiences and claims of hidden evidence, countered by the inability of current science to imagine *HOW* they could be true. That durned "speed of light" thing is quite a nuisance, but most ideas of how to get around it are just fanciful language. "FTL drives" and "wormholes" are great fun for Sci-fi, but like all notions of interstellar travel, the power sources are just as vague.

Let's keep looking....