Aircraft-based observations have made a significant contribution to upper-air monitoring of the atmosphere for many decades. Initially, this contribution was limited to reports from pilots, consisting of little more than radio communications from pilots back to the ground regarding weather phenomena and conditions encountered during flight. Later, with the advent of more sophisticated onboard equipment and avionics, such reports would be standardised and eventually automated into AIRcraft REPorts (AIREPs) of measured weather variables including air temperature and wind speed and direction, provided with positional information. These reports are still made, received and utilised within meteorological applications, through reporting regulations and data exchange arrangements with the International Civil Aviation Organization (ICAO).
In recent decades, the use of the aircraft platform for the automated collection of meteorological data has been considerably enhanced and expanded so as to provide more accurate, more timely and, most importantly a much greater volume of upper-air data in support of data users and meteorological applications, including support for weather-related forecasting and monitoring for the Aviation Industry. The chief source of aircraft-based observations supporting the Global Observing System are currently derived from the Aircraft Meteorological DAta Relay (AMDAR) system. Although, meteorological information derived from aircraft reports supporting the global air navigation system regulated by ICAO, also make a considerable contribution, in particular from systems such as the Automatic Dependent Surveillance and its variants.
Detailed information and guidance for WMO members on aircraft-based observations is available in WMO-No. 1200, Guide to Aircraft-Based Observations.