I am English, and for the English Ageing is considered correct - yet another exception that proves the rule. I wasn't aware that the American preference is to drop the E but in England we generally retain it, even though in almost every other similar situation we would drop it when adding -ing to a word ending in E (fading)

I would read aging as agging. It doesn't make sense to you probably as an American, it hardly makes sense to me either now I think of it.

The standard answer is that both are acceptable. (source: https://www.bbc.co.uk/worldservice/learningenglish/youmeus/learnit/learnitv37.shtml)