How can we arrange a seat for the traveller if the flight is fully booked?

Please be advised that the guaranteed seat benefit is only applicable on intercontinental flights.

A seat in the highest class of Economy Class (Y on KL & AF) is guaranteed on all intercontinental flights – provided the seat request is made outside D-24HRS:
For KL operated flights, please use FN segments in Y if waitlisting is not possible. Seats in the applicable connect class on European flights will be confirmed based on cabin level availability only, i.e. the OPN in the LL/I must show availability. On KLM flights operated by KLM, a robot instantly handles these requests.