I found an I fare (discount business) on AA to London that permits add-ons and end-on-end combinations. Problem is I have no idea what these are. Would someone be so kind as to explain? Is it unusual for the fare rules to allow them?

--AAgoraku

<My apologies if anyone believes I am cross posting; I posed this same question in the AA forum as part of a longer post but did not receive a response to this particular question>