La regola FAA dice:
§ 25.791 Passenger information signs and placards.
(a) Regarding “No Smoking” signs and placards:
(1) There must be at least one placard, or lighted sign, stating if smoking is prohibited. The placard or lighted sign must be legible to each person seated in the cabin.
(2) Lighted “No Smoking” signs must either be operable by a member of the flightcrew or be illuminated continuously during airplane operations. Illuminated signs must be legible under all probable conditions of cabin illumination to each person seated in the cabin.
analogamente, EASA:
25.791 Passenger information signs and placards
ED Decision 2019/013/R
(See
AMC 25.791)
(a) If smoking is to be prohibited, there must be at least one placard so stating that is legible to each person seated in the cabin. If smoking is to be allowed, and if the crew compartment is separated from the passenger compartment, there must be at least one sign notifying when smoking is prohibited. Signs, which notify when smoking is prohibited, must be installed so as to be operable from either pilot’s seat and, when illuminated, must be legible under all probable conditions of cabin illumination to each person seated in the cabin.
Insomma, va bene anche una qualsiasi targhetta fissa purché visibile da ogni passeggero seduto al suo posto. Se il segnale è luminoso o è acceso fisso o è comandabile da entrambi i piloti. EASA richiede la visibilità anche in una cabina buia, quindi implicitamente una targhetta fissa non illuminata non sembra accettabile.