Join Date: Aug 2002
Location: WAS/TYO
Programs: UA 1K, AA EXP (3MM), DL PM, BONVOY TITANIUM, HYATT GLOBALIST, HILTON DIAMOND, IHG DIAMOND AMB, et al
Posts: 5,913
This definitely seems to just be the case of not having SDC inventory. Looking at tomorrow's 7am CUN-PHX flight (AA2569) the OP is trying to change onto, it's currently showing Y3 E0 - so the lack of SDC inventory is not surprising. The OP says it's "fairly empty" but I imagine that's just because the OP is looking at the Y seat map and not the actual loads. Just because the seatmap shows 30+ open seats in Y does not mean the flight is empty. FWIW, I have never had any issues with SDC on company/agency purchased tickets when the SDC inventory actually exists.
-FlyerBeek