Greetings from BCN, the land of Schrödinger's Avios.

I'm currently on a MLA-BCN-LGW connection which started on Vueling and then moves on to BA.

The ticket was booked through Amex (Platinum Travel....which may prove useful if the Gatwick flight gets cancelled like the earlier Heathrow one.) It is all on one PNR, and the Amex portal allowed me to add my IB and BA numbers.

For the first leg I obviously used my IB account as I would not receive BA Avios for a Vueling flight that didn't touch the UK (or Italy). However, I was issued my BA boarding pass in Malta and it too showed my IB number.

The connections desk in BCN said that I could change the number at the gate, but I thought I'd give it a go under MMB whilst I relaxed in the lounge...no luck, it suddenly shows my IB number, but won't let me change it.

So, the question is: can I have two different Frequent Flyer Numbers on two connected legs of a PNR. Up until the point where I checked in, Manage My Booking showed my BA number and Iberia showed my IB number. I was in Quantum FF territory. The act of observing it in MLA after checking-in solidified it as IB.