Originally Posted by violist

Most interesting convo I heard was with a truly incompetent
LA Center controller -

ATC: Delta xxx, slow to yyy knots, present heading.
Delta: If we slow to yyy knots, we will fall out of the sky.

and later:

ATC: United zzz (ours), I need you to make a tight turn
(description forgotten) immediately ...
United: That is outside of the design specifications for
this aircraft.
ATC: Oh.