240 Knts below 10,000 in real life?

Hey all,
I understand the max 250kts below 10,000ft but I’m seeing aircraft departing airports at say 2,500ft at 250kts and then 320kts at 4,774ft. How does this work? Can someone please explain? The second image is of a Boeing 737-8FE.22 05



They are moving at 301 Ground speed. Airspeed is different from that.

More about that here


I believe it’s only in certain areas where there is more air traffic in a confined area. I may be wrong though. As for IF I’m sure it’s there to maintain separation between aircraft at low altitudes and to keep people flying in a controllable manner. With the high traffic we have on IF these speed restrictions really make it easier for ATC and make flying more enjoyable in my opinion.

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I know airspeed is different, they are still flying at 282kts at 7,500ft which is above the rule.


Maybe because they got permission from ATC, or probably they are allowed to fly over the limit if there is not that much traffic.


250/10 is the rule in the US I’m pretty sure. While riding along in jets I have witnessed some times where a controller will grant a plane higher speeds due to an instance needing it in order to keep safe.


… or because the controller is nice. :) The speed restriction can be lifted on ATC discresion. If he wants to be a little nice, he can give that!


I was recently in the DAL tower chatting with them while bringing them some canes. I am also going to visit the tracon here soon. This exact question arose do you ever get planes going over 250 down here. They said not usually. The union manager said when it is its usually due to its needed for safety. I’m sure on VATSIM it’s a bit different.

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I think different rules for different places.

Ok, thanks @Miguel_Ortiz, @bobo2345, @Mats_Edvin_Aaro and @Matthew or the replies! Much appreciated.

Your welcome

Hi, guys, I saw that you have doubts because some aircraft were flying at more than 250Kt (Indicate Air Speed) below 10000ft, first I want to tell you that this is not strange happens for a very simple reason that is the density of the air at sea level.
Air, up to about 250 kt (450 km / h), at sea level and under standard conditions, is considered an ideal (or almost ideal) fluid, which means that the effect of varying density can be neglected in practice. Thus, while the aircraft is flying below 250KT the air is considered incompressible.
some aircraft can change the density of the air, making the other aircraft that pass in this area has a speed above 250kt IAS, I am detailing for you I hope it does not create confusion because this is a very big matter to explain everything here.

I will tell you also because we usually fly at 250kt IAS below 10000ft, the 250KT IAS limit for flights below 10.000 feet serves to standardize and standardize the reading of all aircraft speedometers flying in this airspace, with the guarantee and that when a speed is informed to the control organs, such information is free from any vice of compressibility of the air. Finally, a measure aimed at increasing flight safety at the lower levels.
I tried to explain, I hope you understand, remember a good pilot always learns.

In @ElCapitan profile picture you can see him going 300ias under FL100.
(sorry for tagging)

It depends on the aircraft and airspace. The country you are flying in. High speed below 10,000 ft is only approved for heavies and supers. Only if the ATC allows the aircraft. Nothings done without their permission!
Hope this helps!

Or it can be groundspeed🤔. Flight trackers track there speed by the planes groundspeed

This is what I have heard of, and I also heard that in specific weather and landscape conditions that this is offered to more aircraft if needed. For example when there are very gusty winds, or over mountains

In real live the ATC controller offers the Pilot a higher speed, for example on:

Arrival :

P : Langen Radar, Lufthansa 501 heavy, passing FL180, descending FL110"
A : Lufthansa 501, radar contact, descent via ROLIS25N to 5000, cancel speed restrictions"

Departure :

P : SOCAL Departure, Lufthansa 457 heavy, passing 800, climbing 5000
A : Lufthansa 457 heavy, radar contact, climb and maintain 13000, do not exceed 280 knots

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It depends on two things if your out of an airspace and if your ATC controllers tells you to.

B250 under 10k isn’t as firm of a rule outside the US either. In the US it can only be broken for safety, such as a heavy’s clean safety speed being above 250kts

Also some planes need to fly above 250kts like a 777 for a 12-15 hour flight fully loaded, their minimum clean speed will be above 250kts so they will get approval from atc to fly faster.