Originally Posted by
AirbusA350
Whereas on an Iberia (or Express) operated service, irrespective of whether it’s operating for BA or not, will need masks both ways even if they’re operating to a destination that doesn’t require masks. Hopefully this will change when Spain are expected to review their last remaining mask rules on June 15th. This won’t be an issue if it’s an AY operated wet-lease service though.

I don’t think this is quite correct. I2 flew me to Bordeaux in lieu of BA and there was no mask mandate. I think it must be country- and not airline-specific.