I suppose he could begin the passenger interaction by giving his full name and then asking, "How may I address you?". It would allow the passenger to select his/her preferred choice but would also result in the FA having to remember the individual preference

I prefer being called by my first name, partly because I find it odd when those older than me address me formally. I think it's friendly and more personal, related to another point which is that I'd rather have a happy FA who seems to enjoy the job than a dour, regimented one who appears to be going through the motions devoid of happiness