Generally not true. Indicated airspeed top end is usually highest at low
altitude, but true airspeed capability will rise with increased altitude.
This all assumes no airframe structural limit, which is frequently below the
aircraft's capabilities in commercial designs.

R / John

"Peter Stickney" wrote in message
...
In article ,
"Mortimer Schnerd, RN" writes:
Ian MacLure wrote:
Operationally its irrlevant because the FAA limits speed below 10K
ft to 250Kts IIRC.
As to the actual max speed attainable at low altitude, I believe
you
have it correct.


Agreed. Thicker air equals lower speed. FAA equals even lower speed.

Not necessarily - thicker air also = much more thrust. It's all pretty
much a wash, with a transonic airplane. Usually the TAS in units/time
(mph, kts, km/hr) is higher, but the Mach Number's a bit lower. *The
Speed of Sound is proportional to absolute temperature. It's warmer
near the surface, so there's more mph/Mach Number.

--
Pete Stickney
A strong conviction that something must be done is the parent of many
bad measures. -- Daniel Webster