I was looking at booking some flights to London, and I can see that there is the new fare 'Geneva Economy Light', which is hand-baggage only.
I see that it is possible to later add a bag by upgrading in advance to Geneva Economy flex. What I can't quite get to the bottom of is whether you pay the difference in the price of the two tickets on that day (it seems to be 50 chf difference at the moment for example), or whether it is the difference in what I paid at the time of booking and the price on the day of flying, which can be enormous.
I tried calling Swiss customer support but I'm not sure they understood my query, but seemed to hint at the latter, which means that adding a bag could add hundreds of francs to the price
I just wondered if anyone has used these fares yet and upgraded at a later date?