What should a flight attendant do if they see a passenger smoking in the lavatory?

A flight attendant must prioritize the safety and security of all passengers and crew onboard the aircraft. If a flight attendant observes a passenger smoking in the lavatory, this action violates federal aviation regulations and poses a serious fire hazard. Therefore, the appropriate response is to immediately inform the captain.

Notifying the captain ensures that the situation is handled at the highest level of authority on the aircraft, allowing for any necessary emergency protocols to be initiated. The captain may need to communicate with air traffic control, prepare the crew for potential evacuation, or take other measures to ensure safety.

The other choices do not adequately address the severity of smoking on an airplane. Asking the passenger to leave the plane is not feasible at cruising altitude, and ignoring the behavior can lead to dangerous consequences. While asking the passenger to extinguish the cigarette seems like an immediate solution, it does not adequately escalate the issue to the cockpit, where decisions affecting the entire flight can be made.