If UFO crashes have been covered up for hundreds of years, then why would governments STILL classify such events?

I wouldn't think it would have to do with proving the existence of extra terrestrials. Maybe at one time it would have caused a panic, but would it cause one nowadays? We have been so desensitized from movies, TV shows, and radio shows like Coast to Coast AM. If our government released a statement today stating aliens exist, I'm sure it would stir up the news and social medias, but I think we could handle it. Even the Vadican accepts the possibility of aliens these days.

But what if the thing that's worth hiding is not so much who visited us, but more along the lines of HOW they got here. Maybe we reverse engineered a craft that is able to "bend" space, or manipulate wormholes. Maybe a side effect of such technology could make time travel possible. Could you imagine what would happen if this technology got into the wrong hands? Hell, maybe these UFOs ARE really time machines, and the pilots are us from the future observing the past... Definitely something to keep under wraps.

What if it has to do the the type of fuel / energy they used to get here. If there was anything discovered that would make the use of gasoline look silly, you can forget about that information getting released to the public for a VERY long time. After all, there have been scientists who have mysteriously lost thier lives after getting close to discovering big time alternative energies. Unfortunately, gas will be around for the long haul.

I would love to hear aliens from another world have landed here at one time or another, but if they got here with technologies that our governments don't want us to know about, then I highly doubt any government would ever declassify it.