Looking at booking a cash Y fare and upgrading to J with Avios on IAD to DUB. I will be transferring BA avios to AL.

1. Do I need a specific fare bucket for Y or will the basic economy be okay?
2. I know I need to email to request the upgrade, if there is currently avios availability in business, does that mean the upgrade will clear? I don’t want to buy a flight and then not be able to upgrade it.

Thanks