Hi all, with regards to the big jets eg 747, standard baggage weights are used as it would obviously take too long to weigh everyone and their bags at check in. QF use weights for adults 87kg, children 32kg, infants 10kg or maybe 0kg (from memory) and some carriers use male, female, children, infant weights. I also remember Air NZ having a higher passenger weight figure for rugby teams which was adjusted in the computer system.
My understanding is QF have to limit baggage so pax don't turn up to check in with everything including the kitchen sink.
By limiting the pax baggage weight allows a payload figure to be worked out for the sale of cargo.
eg 747-400ER mtow 412000kg
390 pax booked with bags 39000kg
fuel 160000kg
aircraft weight 190000kg
That leaves 23000kg for cargo sales.
QF overbook flights as passenger "no show" factor can be around 20 to 30. They also can over book cargo weight available as 20-30 passengers failing to turn up for a flight allows 2-3 tonne of weight for extra cargo to be uplifted.
Excess baggage can and does interfere with cargo weights especially on weight critical flights and leaving a 1500kg AKE container behind to get a few extra bags on costs a lot of money. Excess baggage charges are an allowance for any offloaded cargo.
Yes i know, not all flights are weight critical and not all excess baggage results in cargo offloads, it is a good grab for money. I don't always agree with it but airlines have to set some limit for passenger baggage.
Hope this helps,
Cheers