(Edward A. Falk) wrote:

A heavy aircraft at high altitude is approaching what is known as
the "coffin corner" in which slowing down *or* speeding up is a Very
Bad Thing. Being up there and not knowing your airspeed would be very
unhappy-making. But again, the proper thing to do in those
circumstances is to lose altitude, so pulling up would still be the
wrong response.

Found a fascinating blog when searching for the term "coffin corner"
on the intertubes:
http://www.fromtheflightdeckbook.com...in-corner.html

It was written over a year ago, and speculates that Air France 447
encountered the coffin corner.

The report from the French accident investigation agency is a bit too thin
on details to come to any firm conclusions, but it does imply that the
initial zoom climb was initiated by the PF, and not because of weather or
because of a low or high speed stall. There is no doubt that once the
climb was initiated, the aircraft became a victim of a low speed stall,
which the crew were not able to recover from.

The vexing question is why the PF initiated the climb. We will have to
wait for the final report for more enlightenment, otherwise it's just
speculation.