Bag is 24"x10.5"x12" at its widest parts when full. American Airlines states max carry on as 22"x9"x14".

As for your second question, the bag is flexible, and as long as it wasn't completely filled with rigid items, I don't think you would have any trouble at all fitting it into an overhead bin. It wouldn't be any fun under the seat in front of you though.

-Simon