The lavatory should be checked every ___ minutes for cleanliness during a flight.

The correct frequency for checking the lavatory during a flight is every 30 minutes. Maintaining a clean and sanitary environment is crucial for passenger comfort and hygiene. Regular checks help to ensure that the lavatory facilities are in proper working order, stocked with necessary supplies, and free of any mess or unpleasant odors.

At 30-minute intervals, cabin crew can promptly address any issues that arise, such as restocking toilet paper or hand soap, or cleaning any spills. This practice not only enhances the overall flight experience but also adheres to hygiene standards that airlines must follow to provide a safe travel environment.