HI Guys,
I don't work as a F/A (yet), but I am in hospitality. But with an issue like this I think that it goes the same for any job.
My feeling is that you turn up early for work to show you are a dedicated employee, to 'get into work mode' , and to make sure you are all sorted to start your shift. I personally turn up about 15-20 minutes early each shift (and I only live 5 minutes down the road). This allows me to check on memos, catch up with my fellow work mates etc.
I don't see this as being unpaid work. It is just part of keeping my job and my hours and my employee happy with me. But i do feel you are being hard done by if you get a warning if you don't do this!!
love SMILE