My big problem with this is the idea that there are aliens that technologically advanced enough to get here, clearly wish to remain secret, and yet get themselves seen repeatedly. It's a weird combo.
That said, now that we're in an era where pretty much everyone has a HD camera in their pocket, I think sightings will be harder to dispute when they happen.
The best way to look at this is to not assume that there is just one alien race. If there are two, for instance, it could be that one of them wishes to remain secret and mostly has, while the other one doesn't care, and is the reason for nearly all of the sightings.
Or that the aliens like us, are variable in their competence, and every pilot that let's themselves be seen are swiftly assigned to space latrine duty.
