A computing device onboard an aircraft for managing aircraft messages, the onboard computing device comprising: a message receiver configured to receive messages entered into systems on the aircraft for transmission to a ground-based facility; a message analyzer arranged to: i) receive a first message from the message receiver during a current flight; ii) determine for the first message, based on a message type, a maximum allowable delay period associated with the first message to be transmitted during the current flight of the aircraft, wherein the maximum allowable delay period is a maximum allowable delay value added to the time at which the first message was received, representing the latest time that the first message can be transmitted from the onboard computing device system of the aircraft; and iii) receive request information from an operator of the aircraft to set the message type and the maximum allowable delay period in order to manually adjust a transmission of the first message; a mapping data analyzer arranged to generate, based on network map data collected during a prior flight, a forecast of network availability associated with a transmission of the first message; a target network determiner arranged to determine, based on the forecast of network availability, a target network for the transmission of the first message, the target network having a predicted availability at a time during the current flight within the maximum allowable delay period; and a message outputter arranged to output, prior to the end of the maximum allowable delay period, in response to the target network being available, the first message via the target network. a message receiver configured to receive messages entered into systems on the aircraft for transmission to a ground-based facility; a message analyzer arranged to: i) receive a first message from the message receiver during a current flight; ii) determine for the first message, based on a message type, a maximum allowable delay period associated with the first message to be transmitted during the current flight of the aircraft, wherein the maximum allowable delay period is a maximum allowable delay value added to the time at which the first message was received, representing the latest time that the first message can be transmitted from the onboard computing device system of the aircraft; and iii) receive request information from an operator of the aircraft to set the message type and the maximum allowable delay period in order to manually adjust a transmission of the first message; i) receive a first message from the message receiver during a current flight; ii) determine for the first message, based on a message type, a maximum allowable delay period associated with the first message to be transmitted during the current flight of the aircraft, wherein the maximum allowable delay period is a maximum allowable delay value added to the time at which the first message was received, representing the latest time that the first message can be transmitted from the onboard computing device system of the aircraft; and iii) receive request information from an operator of the aircraft to set the message type and the maximum allowable delay period in order to manually adjust a transmission of the first message; a mapping data analyzer arranged to generate, based on network map data collected during a prior flight, a forecast of network availability associated with a transmission of the first message; a target network determiner arranged to determine, based on the forecast of network availability, a target network for the transmission of the first message, the target network having a predicted availability at a time during the current flight within the maximum allowable delay period; and a message outputter arranged to output, prior to the end of the maximum allowable delay period, in response to the target network being available, the first message via the target network.