Ian at FlightRadar24 has harvested some indicated airspeed data from the extended Mode-S data fields:
Additional Extended Mode S data decoded
Flightradar24 has now retrieved and processed extended Mode S data from individual receivers in the area. Unlike ADS-B data, which always contains the same known data points, Extended Mode S may contain data from a variety of fields like aircraft identification, meteorological data, heading, speed, and others. The data sent varies based on the fields requested by the Secondary Surveillance Radar ground stations used by air traffic control.
The data sent via Extended Mode S does not include the Binary Data Selector (BDS) identifying the type of data. Flightradar24 interprets this data using advanced scripts and historical comparative data, but there may be errors in individual frames due to misinterpreted data fields. Overall trends in the data are correct as reported. We have included the raw data, downloadable below.
Included in much of the Extended Mode S data sent by PK8303 were data on Indicated airspeed. The below graph shows the aircraft’s calibrated altitude and Indicated airspeed from 10,000 feet to the final data received.
This altitude plot agrees nicely with the ones previously posted in this thread.
https://www.flightradar24.com/blog/p...-near-karachi/