What utter nonsense - I really can't believe what I am reading. The 747 is limited to around 320kts (I know as that's the red tape on my FS). At '800' kts, the wings would definitely fall off; no sub-sonic aircraft could fly that fast, it would break up.
I have looked at all the commercial jet parameters on my flight sim and none of them is certified for anything near 800kts.