I stand by my comments, Dave, you have your physics wrong.
"when I actually said that IF you feel a sensation THEN it's because the aircraft's speed is changing, not the other way round (I grant you that the sensation may be imperceptible)."
You wrote:
"If you felt a deceleration (i.e. the effect of inertia), all that tells you is that your speed over the ground was reducing."
I'm not pursuing this further, it seems pointless. You've now agreed with my point that it's the speed of the aircraft that's changed, therefore those in that reference frame will feel the change in speed, but then back up your point with the argument that it's ground speed. Sorry, no more time for this nonsenseother than to say:
Thanks to those that gave helpful answers.