I had my Mavic out 2 days ago to see what top speed I could get out of it.  It was just under 40mph in both directions at 38mph.  Fresh battery.  
I've seen some youtube videos where some people have been pulling 50 to 60 mph on the Mavic  I also read some posts where some people think that recent firmware updates my have throttled that higher top speed back or perhaps those 50-60 mph readings were never accurate.  Maybe the firmware simply corrected the speed readout?  

Does anyone know if these 50 to 60 mph runs were accurate or if the firmware update to keep the speed within official spec is true either way?

Thanks.

They were modded. 40 is top speed. A little more with a tailwind.

I got 45.3 MPH with a tailwind.

You need to H it to get that speed but you better know what you are doing because a lot of people wipe out their parms and the MP became a paper weight!

The Max Speed of the Mavic is 40 mph in Sport mode without wind, as you can see the specification. Please visit:  http://www.dji.com/mavic/info#specs  

I got 52 in sports mode (not modded) Must have been the tailwind
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it didn't look fast but the logs don't lie
Ive flown faster at 18Mph
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There was a bug in the GO app last year I think, resulting in incorrect speeds reported.

You are probably looking at video's from this time (when the Mavic first came out).

https://forum.dji.com/thread-70499-1-1.html