This is being discussed on Jeremy Vine on Radio 2 right now, and the 747 pilot who has just been speaking has left me, as SLF, a little confused.
I've a good grasp of physics (which is why I'm not concerned by turbulence, even on the one 'extreme' experience I've had) and can understand the pilot referring to the plane as following a pressure wave. However, he was adamant that the plane does not lose altitude.
If you're in a large metal tube and suddenly hit the ceiling, then that metal tube must surely have dropped by at least around 12 feet. If you're left attached to the ceiling for a few seconds, the tube must be dropping further, surely?
I completely accept that the perception of dropping 'thousands of feet' is out of line, but am I taking this pilot too literally? During extreme turbulence events, what kind of altitude change can there be?