[Serious] What if there's real UFOs but the government DOESN'T know or have as much as some like to think?

There are some good cases - Lonnie Zamora, Cash Landrum, Bentwaters, Rendlesham, ... - and many potentially legitimate accounts by non-famous people. But at the same time, there is an AWFUL lot of dubious science and claims out there. For example, it's really hard for me to believe that something which necessarily has to a) be relatively rare and/or sneaky so as to avoid being trivially obvious by now b) is the product of intelligences and/or alien species far more powerful than us, would c)...