The disclosed embodiments relate to methods for requesting and retrieving aircraft data during flight of an aircraft. This aircraft data can be used to perform additional monitoring of aircraft sub-systems to detect an abnormal condition, and/or to identify one or more sources that are causing the abnormal condition. In one embodiment, aircraft data for one or more relevant parameters can be requested from the ground, measured on-board the aircraft, and stored in a data file that is then communicated back to personnel on the ground. The real-time aircraft data for one or more relevant parameters can then be analyzed to identify the one or more sources that are causing the abnormal condition.