What is the maximum number of passengers that can be checked in per transaction provided the booking is in one PNR?

The maximum number of passengers that can be checked in per transaction within a single Passenger Name Record (PNR) is typically set at 15. This limit is established primarily to streamline the check-in process while maintaining efficiency and organization within flight operations. Setting the cap at 15 passengers allows airline staff to manage boarding procedures effectively without overwhelming automated systems or leading to delays. Each transaction pertains to a specific PNR, which facilitates the handling of requests and changes, ensuring a smoother experience for both the airline and the travelers involved. The other figures mentioned in the options exceed this established limit, thus making them incorrect in the context of the maximum allowed passengers that can be checked in per transaction for a single booking.