for certain nice check-in assistants,they would be quite linient and wouldn't care about an extra 2-3 kg~
also, i had a transit flight,and the flight to amsterdam was delayed due to bad weather in ams~u know what,there wasn't any announcement whatsoever to tell me i had to change my flight since the one leaving from amsterdam would be late!the stupid air france ppl just asked us to wait!
so i approached one of them to ask abt my case, then they realized the problem and changed my flight to a direct flight~
my friend who took emerant (singapore-france,return tic) got an additional free sing-france return ticket when her flight back to sing was just delayed!!!!