A boarding system and a computer-implemented method for boarding a plurality of passengers onto an aircraft, the aircraft having a plurality of seats and each passenger having an assigned seat from amongst the plurality of seats. The boarding system 100 comprises a passenger monitoring system 120 comprising a plurality of monitoring devices, the monitoring devices being configured to determine an occupancy of each of the plurality of seats and/or to determine an occupancy of one or more aisle or boarding tunnel; and a scheduling system 110 configured to control a boarding schedule 112, the boarding schedule 112 assigning each seat to one of a plurality of groups of seats, and comprising a pre-determined boarding sequence for the plurality of groups of seats. The scheduling system 110 is configured to determine time intervals between boarding each of the groups in the boarding schedule 112 based on the determined occupancies of the plurality of seats on the aircraft and/or the determined occupancy of the one or more aisle or boarding tunnel.