I have never had a problem standing by for an earlier flight on KLM out of AMS. The lounge agents will never confirm me, but I just ask politely at the gate toward the end of boarding when the gate agents aren't so busy and have never had a problem getting on board the earlier flight. A couple of times this year, the gate agent was worried there wouldn't be a meal for me, but I just explain I don't need one and they let me one. Coming from the US, it's unheard of to have a meal on 90 minute flight anyway!
or simply not allowed at all. so I had to buy new ticket.
Mainly travel on E/Q/H classes.
So I am very very surprised that you are able to standby for earlier flight WITHOUT having to pay the change fee.
i always receive the standard klm answer: 1. sorry sir that is not possible or 2. the computer does not allow me. 3. we cannot start this practise.
That's what they always tell me at the lounge, but I guess I've been lucky at the gate. I've done it 5 times this year w/o a problem at the gate other than the gate agent's concern about catering. I'm not positive on fare classes, but I think 3 were on Z (discount paid business) and 2 were on upgraded from higher (but not refundable) coach fares.