I can echo Thunderball's experience of having seen a shockwave dancing on a 737 wing en-route from LAX to Las Vegas many years ago.
The wing was up-sun, and I was perched (as usual) right over the point of maximum camber with little to look at but metal. The key seemed to be the polaroid sunglasses I was wearing, because these produced the image of a shock wave about 3 feet away, as clear as any Schlieren picture that I ever produced in a lab (BOAC will vouch for that). Took off the glasses - gone - put them back on again for the show of a lifetime.
My old papers (!) reveal that I subsequently asked the crew the cruise Mach No. - it was 0.76. When a light chop was encountered, the shock wave moved fore and aft by an inch or so, co-ordinated exactly with the "g" of the chop. When the chop turned more severe the aircraft decelerated (Rough Air Speed on a 737-200?) and the shock simultaneously reduced in intensity, slid forward towards the leading edge and disappeared.
I hope I successfully hid my excitement but, belatedly, thank you Western Airlines.
Last edited by D120A; 23rd March 2003 at 23:19.