Ive heard a China Airline's 747 went mach 1 once. Im not sure if it actually went THAT fast, but apparently, they were flying to california across the ocean, during descent, the pilots forgot to disengage the autopilot, the thing stalled, dove, oversped big time, and the pilots pulled like 7 G's out of it to recover

. They got it on the ground with an extremely bent airplane, bloody ears, and a bunch of passengers who probably want their money back.

I just got the story from one of my teachers so i cant say the facts... ;D