A network node of a wireless communications network is provided in a means of transportation, for an aircraft, for ascertaining sources of interference, to a system with such a network node, to an associated method for ascertaining sources of interference of a wireless communications network provided in a means of transportation, for the aircraft, and to a computer program for executing the method. The network node includes an interference-power-ascertaining component, for ascertaining an interference power of an interfering radiation emitted from a source of interference, and a transmitting component for wireless or wirebound transmission of the ascertained interference power to a control device for determining at least one of a direction of the interfering radiation and a distance of the source of interference, including the position of the source of interference, on the basis of the ascertained interference power.