Would love some advice on a similar question. If there is availability on first class for the first leg (FRA - DXB) but not the second (DXB - MLE), if I book first class for the first only and then later first becomes available for the second leg, would I need to pay the full first class amount for DXB - MLE or the remaining balance for a first class flight from FRA - MLE (which would obviously be cheaper)? Thanks so much for your help!