Just wanted to pop on and weigh in here because I couldn't find answers in advance of our trip. We flew DFW-MIA-BCN-FLR this week. AA metal until BCN-FLR but VY ticketed with AA flight numbers.

Before you judge our baggage (lol), please know that we were bringing back wine. When we checked in at DFW, I was able to check in 3 bags as an EXP and my husband could only check in 1 as Plat. It turns out it was the VY baggage restrictions that were limiting him. There was a bit of confusion as the desk agents weren't familiar with Vueling at all and they did try to override the baggage allowance for us. We were able to check the bags all the way through to FLR, which was fantastic.

Our return is more straightforward FCO-PHL-DFW, so we'll just check an extra box for the bag we missed on VY. It was really nice being able to fly directly into FLR. I need more AA availability for that!