New to award flight booking. Trying to book one way AA award CVG to SCL. Found space on LA MIA to SCL via BA site, which will require calling in (assuming this is not phantom). Do airlines ever let you merge a flight say from CVG to MIA into this? If so how do you figure the miles needed?

If CVG-MIA-SCL is available as a "married-segment" award, then you will just be charged the North America-South America 2 award mileage. AA does not charge extra for connections on award travel.

If the CVG-MIA segment is only available as a stand-alone award, then you must add the costs of each award. (In that case, using BA Avios -- if you have any -- for the CVG-MIA segment might make sense, instead of using AA miles.)

How can I tell if it's available as a married segment? I searched for MIA to SCL in BA. I can't in AA.

You call AA and ask.

Edited to add: If CVG-MIA is currently available as a MileSAAver award on aa.com, I would put that flight on a free, five-day hold (do NOT purchase the award), note the PNR, and then call AA to see: 1) whether the LATAM MIA-SCL flight is actually available for mileage redemption; and 2) if it is, whether it can be tacked onto your held CVG-MIA flight to make a single award.

Thanks! That is very helpful.

If it's an upgrade then the answer is no. If it is a buy-up, i.e.the difference in fares then yes.

Any upgrades offered through check-in in the app or via kiosk will almost certainly be considered a LFBU, i.e. the upgrade $$$ won't count towards EQD and you won't receive any additional EQM, etc.

can Economy Web Specials be put on the same itinerary as MileSAAver? it gives me an error trying to do it online but haven't tried on the phone - but then it wouldn't be a web special! if this is possible, does that mean the whole itinerary can't be changed, or just the Economy Web Special leg?

Early boarding
 

What group do families w infants fall under?

Since all AA awards are one-way awards, there really isn't a compelling reason for needing them on one itinerary. I would book the Web special one way and the return in Milesaaver in two itineraries. It just means you have a different PNR on the return trip, and you retain all the flexibility that you have with the milesaaver award on that set of flights.

Pre-boarding with small children must be requested when you arrive to the gate, so be sure to speak with an agent at your gate of departure. You might also find this link useful for other questions about traveling with a small child on AA.

https://www.aa.com/i18n/travel-info/...g-children.jsp

Is it more expensive to change an award flight via the UK reservation number? I just ended up paying about $300 to switch the departure airport of two tickets (still same country), as well as dates. I believe this should have cost me $150+$125 for the second ticket, but instead appears to have cost $150 each (or thereabouts in pounds) plus about $25 more in extra taxes for the new itinerary (so it actually cost me around $325, but ignoring that). I needed to act fast since the flight I was switching to had 2 business seats left in each of the two legs I wanted to switch to, and the hold time on the 800 number for advantage appears to be well over 2 hours (they said they'd call me back when I called... 6 hours ago). It's not the end of the world, but I only realized after I was basically reinstating and getting a new ticket (albeit with the same record locator etc.) for each of us, which, as I say, should have cost $175+ any additional taxes....

I wonder if there's an recourse now?

It should have been $150 for the first ticket plus $25 for any subsequent tickets reinstated to the same account at the same time. So assuming the miles for both tickets came from your account you were definitely overcharged. Just call AA back and tell them you were erroneously charged the full $150 twice and ask them to refund part of it.