Except as provided in paragraph (l) of this section, no person may operate an airplane unless it is equipped with passenger information signs that meet the requirements of § 25.791 of this chapter. Except as provided in paragraph (l) of this section, the signs must be constructed so that the crewmembers can turn them on and off.

Except as provided in paragraph (l) of this section, the “Fasten Seat Belt” sign shall be turned on during any movement on the surface, for each takeoff, for each landing, and at any other time considered necessary by the pilot in command.

No person may operate an airplane on a flight on which smoking is prohibited by part 252 of this title unless either 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 segment. If both the lighted signs and the placards are used, the signs must remain lighted during the entire flight segment.

No person may operate a passenger-carrying airplane under this part unless at least one legible sign or placard that reads “Fasten Seat Belt While Seated” is visible from each passenger seat. These signs or placards need not meet the requirements of paragraph (a) of this section.

No person may operate an airplane unless there is installed in each lavatory a sign or placard that reads: “Federal law provides for a penalty of up to $2,000 for tampering with the smoke detector installed in this lavatory.” These signs or placards need not meet the requirements of paragraph (a) of this section.

Each passenger required by § 121.311(b) to occupy a seat or berth shall fasten his or her safety belt about him or her and keep it fastened while the “Fasten Seat Belt” sign is lighted.

No person may smoke while a “No Smoking” sign is lighted or while “No Smoking” placards are posted, except as follows:

Supplemental operations. The pilot in command of an airplane engaged in a supplemental operation may authorize smoking on the flight deck (if it is physically separated from any passenger compartment), but not in any of the following situations:

During airplane movement on the surface or during takeoff or landing;

During scheduled passenger-carrying public charter operations conducted under part 380 of this title; or

During any operation where smoking is prohibited by part 252 of this title or by international agreement.

Certain intrastate domestic operations. Except during airplane movement on the surface or during takeoff or landing, a pilot in command of an airplane engaged in a domestic operation may authorize smoking on the flight deck (if it is physically separated from the passenger compartment) if—

Smoking on the flight deck is not otherwise prohibited by part 252 of this title;

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 of Hawaii is not entirely within the same State); and

The airplane is either not turbojet-powered or the airplane is not capable of carrying at least 30 passengers.

No person may smoke in any airplane lavatory.

No person may tamper with, disable, or destroy any smoke detector installed in any airplane lavatory.

On flight segments other than those described in paragraph (c) of this section, the “No Smoking” sign must be turned on during any movement on the surface, for each takeoff, for each landing, and at any other time considered necessary by the pilot in command.

Each passenger shall comply with instructions given him or her by a crewmember regarding compliance with paragraphs (f), (g), (h), and (l) of this section.

A certificate holder may operate a nontransport category airplane type certificated after December 31, 1964, that is manufactured before December 20, 1997, if it is equipped with at least one placard that is legible to each person seated in the cabin that states “Fasten Seat Belt,” and if, during any movement on the surface, for each takeoff, for each landing, and at any other time considered necessary by the pilot in command, a crewmember orally instructs the passengers to fasten their seat belts.