Hello
I do recruitment for a very large UK airline, and the very first thing I will say to you is, don't waste your time, or money doing a course of ANY sort, it is not needed, and does not help you get a job within an Airline, it shows enthusiasm for the role, but bears no relevance on the outcome of the assessment day.
As for the Tattoos, If you ensure they are covered and totally 100% not visible, you ought to be fine.
Any more questions, get in touch!
