We have run a wedding week where guests arrived from India, England, the United States and Canada, and another where fifty flew from London, twenty from the USA and seventy-five from across Canada. Coordinating that is a contracting problem, not a booking problem, and it is one of the few genuinely technical things an agency does for you.
Broadly, at ten or more passengers on the same routing. It becomes genuinely valuable at three or more origin cities, because that is the point where managing it yourself stops being feasible and the flexibility starts paying for itself.
It is not always the right answer. Where your guests are spread thinly across many cities with no concentration, or where a large share will use points, individual bookings with a negotiated rate can work out better. We will tell you which applies.
The date passenger names must be submitted, usually 30 to 60 days out. Miss it and seats are released. This is the single most important date in the contract.
Typically a per-seat deposit at signing and the balance at the name deadline. Usually non-refundable, sometimes transferable between passengers.
How many seats you can hand back without penalty, and by when. The airline equivalent of hotel attrition.
We deliberately pick carriers with frequent service on the route, because that is what makes a same-week change possible rather than theoretical.
These are two separate contracts and they get confused constantly. The room block is with the hotel and covers accommodation. Group air is with an airline and covers seats. Different deposits, different deadlines, different change rules, and one does not imply the other.