Fastest I've ever done was "only" 604 kt G/S, (145 kt T/W comp) , but I was flying a CL604 at the time so I thought that was very appropriate! Also was an Atlantic eastbound, Bangor Maine - Luton I think the airbourne time was around 5h 30 (can't remember) I only have the sector time in my book. Quite good for a Chally I think. Good routing close to the great circle, on the jetstream, no delays on arrival. Perfect apart from the fact it was bump bump bump for hours. Trying to eat or drink anything was just aim and hope haha.