Their damn system is so buggy it's been driving me insane.
Often when there is an available J/F award seat in U/Z class on a specific flight (which you know is there because you've already seen it up for Avios redemption on ba.com), it may or may not randomly show as available on iberia.com if you do a one-way search, however if you change your search to a return itinerary by inputting a random return date magically that flight will come up as available.
For example a search for flights from LON to ORD on 26 December shows no availability but if you change it to a return search with the return date say on 15 January it magically shows Avios availability on AA 47 from LHR to ORD in J/F. The same happens if you try bookings to ORD from MAD or another European city, e.g MAD-ORD, their crappy system will show no availability on the 26th on a one-way search but searching for a return look and behold you can book IB3162 and AA 47 for MAD-LHR-ORD.
Totally ridiculous.