A method of assessing safety risk associated with a flight plan of an aircraft , the method comprising: receiving, from the operator of the aircraft, information comprising a flight plan (210-6) and a type of the aircraft, the aircraft being scheduled to implement the flight plan, wherein the flight plan comprises one or more geographic areas over which the aircraft is scheduled to fly and one or more altitudes at which the aircraft is scheduled to fly; determining, based on the flight plan, a plurality of 3-dimensional voxels corresponding to the one or more geographic areas; receiving from a remote system, air surveillance data (210-9) corresponding to the plurality of 3-dimensional voxels; calculating, based on the air surveillance data and the type of aircraft indicated by the information, for each of the plurality of 3-dimensional voxels, a respective probability of collision for the 3-dimensional voxel; calculating, based on the respective probabilities of collision for each of the plurality of 3-dimensional voxels, an air risk value for the flight plan; transmitting, to the operator of the aircraft, a risk assessment indicator based on the calculated air risk value for the flight plan; determining, based on the flight plan including at least the one or more altitudes and the one or more geographic areas, a plurality of 2-dimensional virtual areas at risk to the aircraft when the aircraft is flying according to the flight plan; receiving, from a remote system, population data indicating the respective population density of the plurality of 2-dimensional virtual areas; calculating, based on the population data, for each of the plurality of 2-dimensional virtual areas, a respective ground risk value for the 2-dimensional virtual area; and calculating, based on the respective ground risk values for each of the plurality of 2-dimensional virtual areas, a ground risk value for the flight plan, wherein the risk assessment indicator is further based on the calculated ground risk value for the flight plan. receiving, from the operator of the aircraft, information comprising a flight plan (210-6) and a type of the aircraft, the aircraft being scheduled to implement the flight plan, wherein the flight plan comprises one or more geographic areas over which the aircraft is scheduled to fly and one or more altitudes at which the aircraft is scheduled to fly; determining, based on the flight plan, a plurality of 3-dimensional voxels corresponding to the one or more geographic areas; receiving from a remote system, air surveillance data (210-9) corresponding to the plurality of 3-dimensional voxels; calculating, based on the air surveillance data and the type of aircraft indicated by the information, for each of the plurality of 3-dimensional voxels, a respective probability of collision for the 3-dimensional voxel; calculating, based on the respective probabilities of collision for each of the plurality of 3-dimensional voxels, an air risk value for the flight plan; transmitting, to the operator of the aircraft, a risk assessment indicator based on the calculated air risk value for the flight plan; determining, based on the flight plan including at least the one or more altitudes and the one or more geographic areas, a plurality of 2-dimensional virtual areas at risk to the aircraft when the aircraft is flying according to the flight plan; receiving, from a remote system, population data indicating the respective population density of the plurality of 2-dimensional virtual areas; calculating, based on the population data, for each of the plurality of 2-dimensional virtual areas, a respective ground risk value for the 2-dimensional virtual area; and calculating, based on the respective ground risk values for each of the plurality of 2-dimensional virtual areas, a ground risk value for the flight plan, wherein the risk assessment indicator is further based on the calculated ground risk value for the flight plan. <EOS>