Usually. Although the bathrooms often still get very gross. In many airlines, cabin crew will check the lavatories periodically. This is done for safety, to ensure nothing dangerous has been done in/to the lav (like tampering with the smoke detector), and also to ensure that passengers have a clean lavatory to use.

Cabin crew members are generally responsible for tidying and restocking the lavatories during a flight, but they do not perform deep "washing" or heavy cleaning tasks. Their primary duty is to ensure the toilets remain presentable and hygienic for passengers; this involves picking up stray paper, wiping down the sink and counter, and spraying air freshener. On long-haul international flights, crew members perform "lavatory checks" every 15 to 30 minutes for both cleanliness and fire safety. However, they are not expected to handle "hazmat" level messes or deep-scrub the floors while in the air. If a toilet becomes excessively soiled or "destroyed" by a passenger, the crew will often simply lock it off for the remainder of the flight to maintain safety and hygiene. The heavy cleaning, disinfecting, and waste removal are performed by specialized ground cleaning crews during the aircraft's "turnaround" time between flights. On a few ultra-luxury carriers like Emirates, certain long-haul aircraft may have dedicated "cabin service assistants" whose specific job is to keep the premium lavatories spotless, but this is an exception.