[rudderboost]

Or how about this. The other day we were flying at 38,000 and we had a terrible headwind- about 120kts. I sat there thinking about our outside temps and our weight and decided we should go up to 43,000ft. When we got there the guy in the right seat who is reletively new to the plane said "Oh man, look how much we slowed down." I asked him what he meant since our true airspeed stayed the same and the ground speed went up 30 kts. He replied, "ya, but look at our IAS. (indicated airspeed). It's dropped down 20 kts." After a long discussion about all the measurements of speed (mach, indicated, calibrated, true airspeed and ground speed) it finally hit home when I said if the passengers ask "how long" then thats groundspeed. If the pilot wants to know when will the plane stall, thats indicated. Remember the SR-71 can go many times past the speed of sound and still be 10 kts above stall speed. The plane reacts and flies based on what it feels, with no regard to how quickly the ground is going by.