I believe there are no such things as aliens or
spacecraft that have crashed here however I believe it suits the US
government to perpetuate the myth while officially denying it for
one simple purpose. They have developed (in Area 51) their own
advanced craft based on anti-gravity technology of which there was
a lot of talk about in the 50s but which suddenly mysteriously
died. The genuine saucers that have been seen are in fact these
secret flying crafts and nothing to do with aliens. Even the crash
of 47 could have been an early experimental craft that crashed or,
how's this for an idea, it might really have been a weather
balloon!
Anyway, the conspiracy here is that the government deliberately
feeds certain people, organizations this myth that it is alien
technology to cover up the fact that it is actually
themselves.