Yesterday I was aboard UA104 from LAS to IAD on a 757. About half way into the flight the captain comes on and announces that "normally I don't interrupt with flight information" but we are currently cruising at 37,000 feet with a tail wind of 180kts so the effective ground speed is 748mph.

"If you look out the window you can actually see the speed."

Apparently he was referring to the fact that at that altitude it is difficult to watch your progress over the ground except we were moving extraordinarily fast.

I have to wonder how unusual this is. After over 2M BIS miles, I have never heard this type of announcement before and a pilot friend told me it is very rare.

I should also note that ATC (channel 9) was turned off, unfortunately. We were warned of a bumpy descent as we 'transitioned' through the jet stream, but it was only very light chop. I hope the flights west were not too inconvenienced by the headwinds.