wrote on Mar 11^th, 2009 at 10:31pm:

For one your IAS dosn't truely reflect the true the speed of the aircraft that high up. I'm not a pilot but to slow the aircraft down enough at 32K to deploy the spoilers you would most likely stall out.

The IAS (indicated air speed) is indeed the speed that the *density* of air you're flying in is impacting the aircraft and control surfaces.  If the wings cannot take more than X knots indicated airspeed, you should not exceed that indicated airspeed at any altitude.  Indicated airspeed decreases as altitude increases, because the air pressure also decreases as the altitude increases.

This differs from TAS (true air speed) which is your indicated airspeed corrected for temperature and pressure altitude.  TAS is the speed you're actually moving through the air.

This also differs from GS (ground speed) which is your true airspeed corrected for any effects of the column of air you are moving through (winds), and is the speed you're actually covering over the ground.

You can figure all these out with a few simple readings from your instruments (Altimeter and Outside Air Temperature) and a cheap little gizmo (under $10 for the paper ones) called an E6-B.

This also differs from CAS, EAS... but I digress.