I typically fly UA, and am not familiar with AW's policies re: infants. We'll be flying SMF-LAS on AW; a non-stop flight with a 3 month old trumps a couple thousand miles on UA.
On United you can purchase a seat for an infant for 50% off full fare, but it doesn't seem AW offers a reduced fare for infants. The web site did say that infant carriers (child seats) could not be brought on as carry-on luggage (presumably if you have a lap child) and needed to be checked, however it suggested that they could be _used_ (and not checked) if there was a seat available. Does that imply that if there are seats avail the infant can fly in their own seat for free?
Is there a strategy for getting the infant carrier to the gate in case there is a free seat (I dunno AW's loads between SMF-LAS-SMF, but for the mid-week-mid-day flights we'd be taking I'm sure it isn't full)? We'd be taking the carrier anyways for the rental car and like to make sure it is packaged up well enough to survive checking if it couldn't be brought aboard.