Ten thousand feet ceiling


I check the live tracking screen on a regular basis and have found many aircrafts traveling above 250 knots when below 10 thousand feet. Very often I see aircrafts traveling at 280-320 knots when below this altitude. I was under the impression, that once an aircraft dropped below this altitude, it had to fly at a speed of 250 knots or less. Is this correct?

Also, on the live tracking screen I often see the altitude at which an aircraft is traveling listed as “0 v.” On many occasions this happens while traveling across the ocean or on land still far from the intended destination. How can this be?

Thanks for the anticipated response.



You are correct, 250 knots below 10,000. It is 250 knots indicated airspeed. The pilot will see 250 on the airspeed indicator and (with a 70 knot tailwind) ATC would see a 320 knot groundspeed.

Hope that helps.


Thanks for the response, Falcon 1. Do you know the answer to the second question regarding altitude? Sometimes instead of “0 v” it is just plain “0.”

Thanks very much.



The altitude anomaly you mentioned is likely related to the issue described in a number of previous posts such at the one available by clicking here.

The use of “^” and “v” indicates a climb or descent from the previous record in the track.

Also, it is my understanding (I’m not a pilot) that the 250 knot indicated air speed limit under 10,000 feet does not apply to flights in controlled airspace (Classes A, B and C).

If you haven’t already, you should consider carefully reviewing the FlightAware FAQs available at the top of each page by clicking on Questions/Answers.


Slight corrections to the previous answers. The max allowed indicated airpseed is 250 kts. below 10,000 feet, all airspace. Same rule all over the world as far as I’ve ever seen. Some countries allow the controllers to waive this but not in the US. (kinda fun to drive up to the outer marker at 300, but that’s another story). 250 IAS will get you about 280 TAS at 10,000 ft., depending on temperature, then apply the headwind/tailwind to get the ground speed seen by the ATC radar and forwarded here.

There was a test of waiving the speed on climb out years ago, but it was dropped when aircraft were driving out of the side of the TCA (class B nowadays) instead of the top when they should have been at or above 10,000 anyway.

The altitude anomaly has been around for years, ever since encoding altimeters anyway. I once had an avionics guy try to use plain English to explain why. Something to do with the difference in the output signal between, say, 5000 feet and 5100 feet being pretty small. Throw in the other usual electrical stuff and it’s a miracle we don’t fall out of the sky.

Once in a while you will see an airplane that has just become airborne showing the cruise altitude that is filed in the flight plan, again that is something that shows up for one or two sweeps of the radar and is updated with the actual altitude as soon as the computer gets a full report from the transponder and processes it. Since FA does not update that frequently it will be a few minutes and a few miles before you get an actual altitude shown here.

3 days to a cold one!


Also, it is my understanding (I’m not a pilot) that the 250 knot indicated air speed limit under 10,000 feet does not apply to flights in controlled airspace (Classes A, B and C).

I need a CFI to verify this for me, but I believe the speed limit is 250 within class B and C airspace, 200 underneath the shelves of class B and C, and inside class D and within 4nm under 2500agl in class C.


Had to look it up just to be sure. thats what happens when you never fly below class B airspace any more!!

91.117 Aircraft speed.

(a) Unless otherwise authorized by the Administrator, no person may operate an aircraft below 10,000 feet MSL at an indicated airspeed of more than 250 knots (288 m.p.h.).

(b) Unless otherwise authorized or required by ATC, no person may operate an aircraft at or below 2,500 feet above the surface within 4 nautical miles of the primary airport of a Class C or Class D airspace area at an indicated airspeed of more than 200 knots (230 mph.). This paragraph (b) does not apply to any operations within a Class B airspace area. Such operations shall comply with paragraph (a) of this section.

© No person may operate an aircraft in the airspace underlying a Class B airspace area designated for an airport or in a VFR corridor designated through such a Class B airspace area, at an indicated airspeed of more than 200 knots (230 mph).

(d) If the minimum safe airspeed for any particular operation is greater than the maximum speed prescribed in this section, the aircraft may be operated at that minimum speed.


Can we hear it?


lol, well it requires an airplane that slows down quickly. Like the tip tanked G2. Anything with a clean wing I think you would need about 10 miles from touchdown.
You have to be level and realistically in VMC. I sure wouldn’t want to try it in the clouds. The OM might not really work, but if you have about 2 miles of level flight before hitting the glide slope it works. Just. Obviously power goes to idle and flaps and gear come down as soon as you hit the speeds.
Following the Goodyear blimp makes it a bit tough.


300kts to the marker? LaGuardia, right? :smiley: Every day is an adventure here in the New York Metro airspace.


Actually the speed limit gets waived pretty much anywhere in the Middle East regularly except Dubai where it is so busy you get slowed down early. Jeddah, Riyadh, Bahrain are all busy enough that most of the time you end up back at a more normal 210 by the time you are within 15 miles of the airport. But sometimes you are number 1!! I don’t push it with passengers but on those empty legs watch out.


Thanks for the clarification. I held an understanding that ATC (U.S.) had limited discretion for waiving the max airspeed. However, that must have been something I read related to jurisdictions outside the U.S. A reading of the Reg at 91.117 certainly clears that up.

With that Regulation in mind, 91.117(d) might be another explanation of the original poster’s query regarding speeds in excess of the max. Are there some aircraft configurations that would have a minimum safe airspeed in excess of 250 KIAS under 10,000 feet?


US Air Traffic Controllers must authorize an aircraft to operate above 250kias below 10K if the pilot says that a higher minimum safe speed is required. I’m sure some 747s and other heavies have a minimum higher safe speed during climbout.

The original question’s answer . . . 280 to 320 groundspeed (what you see on Flightaware) below 10000 is pretty common . . . 250kts at 10000ft is around 280 knots TAS, plus a 30 knot tailwind makes a groundspeed of 310.


Yes, there are exceptions to the rule as you guys point out. I was thinking about more normal operations.

Once in Frankfurt I heard the controller slowing everybody to “minimum clean speed”, i.e. no flaps, on the arrival while still 40-50 miles from the airport. This meant anything from 180 to 210 for most aircraft except one Lufthansa 747 said that would be 255, the controller said that was fine. They passed under us about 25 miles from the airport like we were going backwards. We all pretty much kept that speed right up to the final approach.

On climb out from the London area it’s fairly normal to get “no speed restriction” from ATC after you are pointed in the direction you want to go. When they say that they mean speed up. now. That generally happens around 4-6,000 feet after most of the vectoring has happened.


Yep!! lots of fun “November &^, Cleared High Speed” (w/appropiate accent) is always the hint go fast or plan to hold.


you need to go fast to escape the missiles…


A couple interesting exceptions with regard to US ATC.

7110.65 7-5-2
faa.gov/airports_airtraffic/ … qnI37aJACK


  1. A pilot operating at or above 10,000 feet MSL on an assigned speed adjustment greater than 250 knots is expected to comply with 14 CFR Section 91.117(a) when cleared below 10,000 feet MSL, within domestic airspace, without notifying ATC. Pilots are expected to comply with the other provisions of 14 CFR Section 91.117 without notification.

  2. Speed restrictions of 250 knots do not apply to aircraft operating beyond 12 NM from the coastline within the U.S. Flight Information Region, in offshore Class E airspace below 10,000 feet MSL. However, in airspace underlying a Class B airspace area designated for an airport, or in a VFR corridor designated through such as a Class B airspace area, pilots are expected to comply with the 200 knot speed limit specified in 14 CFR Section 91.117©. (See 14 CFR Sections 91.117© and 91.703.)"

I added the underlines. Also people seem to think of controllers as FAR police. Really in the end all controllers really care about is separation.