(a) The never-exceed speed VNE must be established so that it is --

(1) Not less than 0.9 times the minimum value of VD allowed under §23.335; and

(2) Not more than the lesser of --

(i) 0.9 VD established under §23.335; or

(ii) 0.9 times the maximum speed shown under §23.251.

(b) The maximum structural cruising speed VNO must be established so that it is --

(1) Not less than the minimum value of VC allowed under §23.335; and

(2) Not more than the lesser of --

(i) VC established under §23.335; or

(ii) 0.89 VNE established under paragraph (a) of this section.

(c) Paragraphs (a) and (b) of this section do not apply to turbine airplanes or to airplanes for which a design diving speed VD/MD is established under §23.335(b)(4). For those airplanes, a maximum operating limit speed (VMO/MMO-airspeed or Mach number, whichever is critical at a particular altitude) must be established as a speed that may not be deliberately exceeded in any regime of flight (climb, cruise, or descent) unless a higher speed is authorized for flight test or pilot training operations. VMO/MMO must be established so that it is not greater than the design cruising speed VC/MC and so that it is sufficiently below VD/MD and the maximum speed shown under §23.251 to make it highly improbable that the latter speeds will be inadvertently exceeded in operations. The speed margin between VMO/MMO and VD/MD or the maximum speed shown under §23.251 may not be less than the speed margin established between VC/MC and VD/MD under §23.335(b), or the speed margin found necessary in the flight test conducted under §23.253.