Hi
I have yet another question! Last year I watched a programme where James May went up in a U2. He explained that at FL700 the plane was flying in "coffin corner" and that the difference in IAS between the stall and the max speed was only 10 knots. I understand that it's due to the very low air pressure at such heights. As Concorde could fly up to FL600 I wondered what this safe airspeed window was during the cruise/climb phase of flight and if this window was framed by the air pressure and/or the CofG position?
Once again thanks to everyone for such great answers and also for the background information.
Regards
Nick