We know aliens exist, as there is too much proof of flying craft that we could never design for the next 500 years, at least. It’s only a question as to what it really could be.
The Bible only gives us what we need to know. We don’t need to know anything else about life outside this planet, for now. I do believe that, in eternity, the universe will be ours to explore and everything in it for us to get to know, what ever that will end up being.
I worked on UAV's back in the late 80's early 90's. That wasn't aliens, it was top secret technology. Look at Tonopah Test Range, where the F-117A was test flown from. Area 51, etc.
There is no intelligent life that has flown here from other planets. It just isn't possible. So, Occam's Razor and all that.