re: just beyond current technology...
That's a good question. I know a lot of reports are scattered around the web, and I'll look for them. This site mentions the flying dirigibles around the turn of the century, and there are some great illustrations of what's been seen here in the US since the 1940's.
Wouldn't it be interesting if what witnesses were seeing were actually glimpses of the <future>, as if there are dimensional holes in time/space we have access to?