Why would any pilot want to take an aircraft beyond it's defined envelope?
Want to go supersonic in a 747, go fly down wind in the jet stream, as previouly suggested.
I don't believe anyone has suggested taking a 747 supersonic!
It's an interesting discussion though. I seem to recall it got a mention in the book,
'Handling The Big Jets'.
From what you posted Mustangsally, you're the only one here who has
nudged the envelope! 