400 Knots below 10,000 MSL


Well-Known Member
Hi Folks:
On Sunday night I came home from Tampa to JFK via jetBlue. I noticed on both flights, via the seat back flight tracker, that our groundspeed was well over 400 mph by the time we got to 10,000. Does the 250 knot limitation apply to airliners? I am just a VFR private but I thought that applied to all aircraft except military. As a matter of fact we were like 350 mph(300 knts?) before we even hit 5000, and I don't think we were in a 50 mph direct tailwind. Any explanation?
Anyhow, the A320 is a NICE airplane. Thanks!



New Member
The 250 KIAS limitation does apply.

I have a couple of guesses:

1. The limitation is in indicated airspeed, but the flight tracker displays groundspeed. I have seen some strong winds in the past couple of weeks, so this is most likely. 400 mph is roughly 342 knots. A one hundred knot wind at 10,000 is not unheard of.

2. With an indicated airspeed of 250, you will also see true airspeeds greater than 250.

3. Since ATC cannot read an aircraft's indicated airspeed, the pilot may have been fudging. If he was number one for the runway, ATC may have told him to keep his speed up and not called him on a variation of a few knots.

4. The pilot may have had a brain fart and filled out a NASA and JSAP form following the flight.


Well-Known Member
Yeah depending on the day it's very possible to have a 50 knot tailwind at 5000.

Also - those 'flight tracker' aka AirShow, aka cabin info systems aka whatever you call them have a tendency not to update all that often and sometimes aren't that accurate. I was in the back of a Delta 737-800 and watching that system and it was coming up with some wacky numbers.



If specified, this will replace the title that
Could have been several things.

1) MPH reads signifigantly higher than Knots - which is why aircraft manufacturers list the speeds of their aircraft in MPH in the sales brochures.

250kts = 300mph +/-

2) A tailwind would affect the displayed groundspeed (add in the tailwind with the MPH figure and you could, maybe get the 400mph you saw - it'd be an awfully stiff tailwind at that altitude though)

3) Or, ATC could have issued a waiver for the speed restriction. They are rare but it can and is done occasionally.

4) Most likely it was probably just an error in the software.

I dunno ... I just buzz an old beat up twin around the sky so whadda I know?


New Member
No, they go that fast.

jetBlue and several other carriers file over the AR routes to avoid "traffic flow." Since these atlantic routes are offshore, past the ADIZ, the 250 kt speed limit does not apply.

I remember jumpseating with a jetBlue flight going in to FLL and seeing them steaming in at 320 KIAS at 7000', until we got closer to shore.


Well-Known Member
Thanks guys for the response:
I mostly noticed this on climbout. Even leaving Tampa(not over the Atlantic) We took off to the north so I dont think it was a tailwind(and climbed out to the north, and cruised as such, and landed at JFK to the north, it was as if we made no turns the whole flight). The pilot said that the flight tracker was tied in to the airplanes satellite nav system. Taxiing showed 20mph and alt 16 feet. After takeoff we got to 3000 and I looked at the groundspeed and I was thinking 'this thing is accelerating faster in climb than on the takeoff roll).' The tailwind makes sense, but only if it is perfectly 180 and VERY strong, which I dont think would be the case both flights(and considering takeoff direction).
Overall it was my first time on an a320 and it seemed strange. When the spoilers came up during descent you didn't feel/hear the normal rumble, and everything else was super smooth. From these 2 limited flights, and a passenger perspective, I can tell you Airbus puts out one good product.
Thanks Dave, Giants Fan and others for your prompt replies.



Well-Known Member
More than 12 miles offshore of U.S. is what this situation is. Another time is for heavy larger widebodies, where our min maneuver speed is faster than 250kts, the fastest civilian being the MD-11 which is 289kts indicated at max takeoff weight.


New Arizona, Il Duce/Warlord
Staff member
Our clean speed on the MD-90 is often up to 260 knots below 10,000 feet.


Well-Known Member
That Douglas wing seems to need a lot of air moving over it to hold the airplane up compared to other manufacturers!

Compare to the A-380, not sure what clean max takeoff weight speeds are, but would guess under 250kts at 1.3 million pounds. I do know that the max landing weight final approach speed at 941,000 is projected to be 140kts! Compare that to the MD-11 at 481,500 at 167kts!


Resident Knucklehead
Well, the other thing is, if that is getting the information from RLM or FlightTracker, there is a huge tendency for erronious reading. We use RLM in the dispatch office and at times it gives us some WAAAAAY goofy readings.

The other day I had a CRJ abort a takeoff out of IAD to ATL, but apparently the RLM software caught a sweep of him on the ground rolling. The airplane went back to the gate, but the little airplane icon continued on its merry way on a southwesterly heading at 300 feet (drilling holes through the Blue Ridge mountains) and 100 knots for the next hour, until it finally was airborne and the icon "snapped back" to the true information. About a 6.4 on the old effedup-o-meter.

In any event, that's probably why you appeared to be smoking along at low alts.



Sitting in the median
Might have just been the readout. We were doing 240 KIAS heading into LEX today, but had a pretty huffin' tailwind. Our TAS was about 310, and our groundspeed was around 350. Translate that into MPH, and it's 402 MPH. So you can see how this would be confused.


Well-Known Member
Thanks folks for all the inputs. A wise man once said "a good answer is one that leaves you with more questions!"


Well-Known Member
ATC can approve >250 kts over Houston! It's a blast to be doing 320 indicated at 4000 feet! By the title of the post I though maybe that's where you would have been!