As far as my knowledge goes: There is a 250 kt speed limit under the altitude of 10.000 feet. This screenshot seem to show an aircraft below 10.000 feet and traveling at 285 kts at the time i captured the screenshot.

I don't think this aircraft posed any threats to other aviation traffic as there is no other traffic in the airspace. I was just curious.


Shortly after: I see this aircraft taking off from the same airport. Doing the same thing as the first plane.

  • $\begingroup$ The speed in flightradar24 is IAS? $\endgroup$
    – orique
    Commented Jan 23, 2014 at 11:56
  • 1
    $\begingroup$ Well it is a ADS-B feed from the aircrafts transponder. So im not sure if it is airspeed or ground speed. $\endgroup$ Commented Jan 23, 2014 at 11:58
  • $\begingroup$ It can be either: adsb.tc.faa.gov/WG3_Meetings/Meeting30/… $\endgroup$
    – Jon Story
    Commented Feb 10, 2015 at 13:22

2 Answers 2


First of all, this aircraft was flying in Europe, not in FAA land. In Europe there is no general limitation to 250 knots below 10000 ft. There is no EASA airspace restrictions, every country has their own set of rules. There are airspaces that have speed restrictions below 10000 ft, others don't and sometimes aircraft are allowed to go faster than 250 knots with ATC permission.

Secondly, the 250 knots is an indicated airspeed limitation. At 10000 ft, 250 KIAS (Knots Indicated Air Speed) will be approximately 289 KTAS (Knots True Air Speed). And then there is the additional effect of wind. With a strong tailwind you can exceed 350 knots ground speed while still flying below 250 KIAS.

Thirdly, the data in the image you linked is provided by ADS-B. ADS-B can transmit either ground speed or air speed. Under the European ADS-B mandate, aircraft must transmit ground speed, not air speed. But since this mandate will not affect this particular aircraft until December 7, 2017 it might very well be transmitting True Air Speed.

Note that ADS-B data is not purely derived from GPS. The Mode S transponder which provides the ADS-B out functionality on this aircraft is attached to various data channels and is getting Indicated Airspeed, barometric vertical rate. In fact ADS-B vertical rate is preferably from a barometric source.


To add to the above answer, if the aircraft is heavy and has a minimum clean (flaps up) speed above 250 KIAS, then it can request and receive an exemption from the 250 below 10k rule, in any country where it applies. The pilot makes the request long before beginning the departure and, unless there is an actual safety threat from the exemption, it is authorized. Track some of the heaviest departures (Air India, Emirates) from the US and you'll see that after the second stage of climb (acceleration to flaps retraction) they attain a speed greater than 250 KIAS and greater than neighbouring non-heavy departures.


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