Yeah, I'm wondering if it might be some sort of ancillary fee (that just happens to have posted on the same date as a ticket). I've been flying United as my primary carrier since I moved to the US 15 years ago, and never ever seen either of these fees charged separately, nor have I ever seen them double-charged. The only thing that comes close is I've seen (commonly) farelock fees be authorized more than once, but even then, the charges have never posted incorrectly. I was thinking maybe in-flight food or beverage, which one can forget about if they don't charge right after the flight (which still happens on occasion even with the iPhones...before the iPhones, I remember commonly having so much time between a purchase and it actually charged, that I at times couldn't recall what the charge was for since it had been weeks), but I think onboard food is all even dollar amounts.

I also concur with some of the previous posts on here, about it maybe being a farelock charge, wifi charge, or something of that nature. Also good advice to see if the ticket number appears in the details of the charge (don't know about AMEX, but my cards via Chase always include the ticket number in the details....I believe it should no matter the card), and seeing if it matches the ticket number. Going from there, you can probably also call UA, let them know you have a charge you don't recognize, and if you provide them with the 016 number referenced, they should be able to give you details on what its for.