I saw an indicated 800mph groundspeed once via the IFE flight tracker, though I'm not sure I believed it. The pilot reported 225mph on our tail, which is the highest tailwinds I've heard on one of my flights. I don't recal whether is was a 777, 747, or 757. I believe the 747 cruises at about 570 and maxes at 615, iirc.

700 is well above typical, but isn't all that outrageous - I doubt this was the first Airbus to ever go that fast.

EDIT: 700mph is 608 knots. see http://www.groundspeedrecords.com/da...commercial.htm for plenty of 700mph Airbi. It looks like 763mph for a 320, 845mph for an Airbus, and 847 for a current commercial jet (a 747) are the fastest documented.