An increasing number of aircraft enthusiasts and spotters around the world have been using receivers portable Mode-S/ADS-B receiving station and relative software for real-time tracking of flights on a sort of radar screen. Mode-S employs airborne transponders to provide altitude and identification data, while ADS-B adds global navigation data typically obtained from a GPS receiver. An aircraft equipped with such systems periodically broadcasts position and other relevant information to potential ground stations and other aircraft with ADS-B; a solution similar to the Automatic Identification System (AIS), used by ships and Vessel Traffic Services.
A few websites give the visitors the possibility to track flights flying in Europe, N. America, Asia and Australia, by means of many remote stations (something similar to the cloud computing). On Apr. 11, 2010, just before midnight, I was following the tracks of the flights landing in Rome Fiumicino and Ciampino airports at http://www.flightradar24.com/. The weather was poor. My attention was struck by a weird callsign: @@@@@@@@. It was obviously an error, but when I selected the aircraft I saw that it was a Ryanair B737-800, with registration EI-DCP, that was about to land in Rome Fiumicino after (according to the track that you can see below) attempting twice to land in Ciampino in bad weather. Noteworthy, most probably to wait for the weather to improve, the aircraft, after the first missed approach headed SW over the Tyrrhenian sea.
