I'm just curious, when a plane is given no speed restriction by ATC, does that mean that the plane can go as fast as the crew want to go, or do they still have to follow the 250kts limit under 10,000 ft?Thanks,Francois

Hi Francois,The crew has to obey the 250 knot speed limit, unless the minimum safe speed for the aircraft requires that they go faster or unless they declare an emergency.Below 2,500 feet AGL and within 4 nautical miles of a Class C or Class D airport, the speed limit is 200 knots, unless ATC says you can go faster or unless the aircraft requires a higher minimum safe speed. The 200 knot speed limit also applies when operating underneath Class B or in a VFR corridor through Class B.John

Other than if they declare an emergency, aircraft can only exceed tbhe 250 knot speed limit due to 'minimum safe speed' requirements if it's been pre-approved by ATC. You can't go zooming around at 5,000 and 500 knots VFR on the grounds that you can't safey fly slower. If you've got a plane that needs that much speed, your flight routes must be cleared through ATC.(Different rules, of course, for the military)Richard

Note that the previous replies refer to the U.S.A. (correct me if I'm wrong). In Sweden, where I live, only certain TMAs have the 250 kt speed limit (for IFR traffic) and if ATC waives the limit there is no speed limit at all. As far as I understand this is how it works in most of Europe - if ATC says "no speed restriction", there is no speed restriction!Martin767 fetishistIt's a lot like life and that's what's appealing

If the controllers say "no speed limit", than the aircraft is free to go as fast as they want, even if below 10,000. Houston used to be one such area in the USA where the controllers regularly allowed pilots to go faster than 250kts below 10,000, while inside the Houston B airspace. The experiment ran for several years and ended last January. I do not believe that the "no speed limit" procedure will be done anywhere else in the USA, since the experiment did not show any significant increase in airport capacity, and safety groups objected to the increased risk from birdstrikes and excursions underneath B airspace.

Thanks for your feedbacks guys, much appreciated,Francois

"If the controllers say "no speed limit", than the aircraft is free to go as fast as they want, even if below 10,000." Hunh?, the 250 knot below 10k is still in effect in the United States unless I missed a change to the 7110 (unless operationally restricted to a higher speed and ATC is notified "Gonna need 270 in the climb..."). One of the tricky ones is not on departure but arrivals-a few pilots have been told to maintain 170 KIAS and then cleared for the approach and still think they have to maintain 170 thru the approach. Really messes up the approach to come screaming down past the marker trying to slow up, get down and be established. I want to say it was SWA in California....but not sure.When cleared for the approach in the United States the previous speed restriction comes off and the pilot operates the aircraft per profile.Tim757

That was the phraseology the controllers at Houston Intercontinental used with us. For several years, we were allowed to exceed 250kts below 10,000 when departing KIAH. Yes, below 10,000. The experiment ended last January. I don't believe NW uses 757s to KIAH, so you probably missed out on the fun we were having here unless you worked on the DC9 or Airbus at some point the last two or three years.Otherwise, everytime I've been assigned a speed in excess of 250kts when I was below 10, the controllers have always qualified the statement with "leaving ten thousand."

Yup, I missed that fun, but read the results of the trial in a couple of industry/ALPA pubs."If it isn't one thing, its another...."Tim757