Tattoos and future pilots
I recently applied to a major carrier. In the application form I was asked if I had any visible tattoos and in the interview I was just asked if I had any. In both cases I was able to answer no.
Employers can and will discriminate against someone who has them.
At a very minimum they must be covered at all times, ideally in today's airline world you shouldn't have them in any spot that could ever be seen.