Just my two centavos on Gol, which is probably among the most opaque FB partners.
This week I flew GIG-EZE on G3 in Economy. This was not related at all with AF/KL – no AF or KL flight number, booking done through Lufthansa as part of a multi-city trip.
I added my FB number when doing online check in on G3’s app. I wasn’t able to select the Comforto seats but my boarding pass showed “AFKL Platinum Priority” and zone 1 boarding.
At GIG the check in staff told me to use the Premium desk. There was a glitch on my booking – my whole itinerary included a checked bag but the agent couldn’t see it on her system. She asked her supervisor and told me “I still cannot see your bags on the system but as a Platinum you are entitled to checked in luggage anyway”. She even added a Priority tag before sending it off. I didn’t try to enter the lounge but I suspect it wouldn’t have been possible.
Overall a very nice surprise. I wasn’t expecting any Plat perks on this flight when I booked it.