Hmmm...Flower, thank you for your comments. That is always my fear, that the person who does the hard work is not the one who benefits. Does tipping personally mean that passengers who want the employee to get the tip should directly hand it to the person? Rather than leaving it for the person or letting it be charged to the account? And if you give it directly to the person would they then get to keep it themselves rather than splitting it, perhaps not fairly?
If you can answer that would be nice and might affect whether I allowed the charge to be placed on my account or took it off and gave the tip personally. Although that would make me somewhat uncomfortable, I would prefer it if the person who worked so hard benefitted. Don't get yourself into trouble, though. It's not worth your losing your job to answer a question from a stranger.