14 CFR § 135.127 - Passenger information requirements and smoking prohibitions.
(a) No person may conduct a scheduled flight on which smoking is prohibited by part 252 of this title unless the “No Smoking” passenger information signs are lighted during the entire flight, or one or more “No Smoking” placards meeting the requirements of § 25.1541 of this chapter are posted during the entire flight. If both the lighted signs and the placards are used, the signs must remain lighted during the entire flight segment.
(b) No person may smoke while a “No Smoking” sign is lighted or while “No Smoking” placards are posted, except as follows:
(1) On-demand operations. The pilot in command of an aircraft engaged in an on-demand operation may authorize smoking on the flight deck (if it is physically separated from any passenger compartment), except in any of the following situations:
(i) During aircraft movement on the surface or during takeoff or landing;
(ii) During scheduled passenger-carrying public charter operations conducted under part 380 of this title;
(iii) During on-demand operations conducted interstate that meet paragraph (2) of the definition “On-demand operation” in § 110.2 of this chapter, unless permitted under paragraph (b)(2) of this section; or
(iv) During any operation where smoking is prohibited by part 252 of this title or by international agreement.
(2) Certain intrastate commuter operations and certain intrastate on-demand operations. Except during aircraft movement on the surface or during takeoff or landing, a pilot in command of an aircraft engaged in a commuter operation or an on-demand operation that meets paragraph (2) of the definition of “On-demand operation” in § 110.2 of this chapter may authorize smoking on the flight deck (if it is physically separated from the passenger compartment, if any) if -
(i) Smoking on the flight deck is not otherwise prohibited by part 252 of this title;
(ii) The flight is conducted entirely within the same State of the United States (a flight from one place in Hawaii to another place in Hawaii through the airspace over a place outside Hawaii is not entirely within the same State); and
(d) No person may operate an aircraft with a lavatory equipped with a smoke detector unless there is in that lavatory a sign or placard which reads: “Federal law provides for a penalty of up to $2,000 for tampering with the smoke detector installed in this lavatory.”
(f) On flight segments other than those described in paragraph (a) of this section, the “No Smoking” sign required by § 135.177(a)(3) of this part must be turned on during any movement of the aircraft on the surface, for each takeoff or landing, and at any other time considered necessary by the pilot in command.
(g) The passenger information requirements prescribed in § 91.517 (b) and (d) of this chapter are in addition to the requirements prescribed in this section.
(h) Each passenger shall comply with instructions given him or her by crewmembers regarding compliance with paragraphs (b), (c), and (e) of this section.