Aircraft need to be kept clean for service, to maintain brand, and prolong aircraft life.

Aircraft see heavy use every day, and need to be kept clean. There is even more of a focus on this since the pandemic began. With tight schedules and often fast turnarounds, airlines need well-defined cleaning processes that can fit in with operations. This includes regular internal cleaning between flights, as well as heavy external cleaning during maintenance periods.

Let's start with the outside of the aircraft. Cleaning the fuselage of an aircraft is important. Of course, it makes the aircraft look better (important for the airline's brand). Removing dirt and debris also helps the aircraft's aerodynamics and efficient performance. It also helps show up any damage on the skin - for this reason, many airlines will schedule external cleaning just before maintenance checks.

Washing an aircraft is more complex than it first appears. Sensors and inlets must be covered, and there is then a large area of the fuselage to access and clean. It is time-consuming.

Lufthansa, for example, claims it takes between 8 and 24 hours to wash an aircraft, and United Airlines report taking around five hours with a crew of up to five people to wash a widebody. This is costly both in resources and having the aircraft out of service. Not surprisingly, therefore, cleaning is certainly not a daily task. Airlines report washing every two to six months - often in line with the A or B check maintenance schedule.

AIrcraft can be washed with water and detergent, or dry washed. Wet washing usually involves high-pressure water jets and specialized detergents. Improvements in detergents is cited as a reason for some airline being able to lessen cleaning frequency.

Dry washing is a newer technique used by some airlines. This involves applying cleaning agents to the surface, then removing with mops or wipes. This uses much less water - great for green credentials and cost - and can be carried out in any location. Emirates is a big adopter of dry washing, and claims it saves 11.7 million liters of water per year (as reported by travelradar.aero).

The engines are obviously very different from the rest of the exterior and will be cleaned differently. During standard wet washing, engines will be plugged or covered to prevent damage. Again, this is not a very frequent task and will usually be done alongside heavy maintenance checks.

To clean inside engines, fresh water is pumped into the turbine and cycled through. Only once the water coming out of the back of the machine is clear is the cleaning considered done. Solvents can be used to break down any particle build-ups.

Unlike the external fuselage and periodic cleaning, the interior aircraft cabin needs to be cleaned after each flight. This varies of course between airlines and flight types. After a short flight with a low-cost carrier, the airline may just remove obvious dirt and rubbish between flights. More thorough cleaning may then be carried out at the end of the day's service. After a long-haul flight, a widebody will need a much more thorough clean before re-use. This is not just to do with cleanliness - it is about customer expectations too.

Cabin cleaning has changed a great deal due to COVID-19. This is likely to remain the case for some time. Many airlines now have more thorough cleaning regimes, some of which is guided by IATA.

Light cleaning will involve tasks like collecting rubbish, changing linens, and wiping surfaces. A more thorough daily or widebody clean will involve vacuuming, checking seat coverings and more thorough disinfecting.

During and after COVID this cleansing has become more intense, involving thorough cleaning of surfaces and/or fogging of the cabin. There have been many other cleansing initiatives introduced as well, such as United Airlines' methods to use robots to apply an antimicrobial protectant spray to cabin surfaces, and using ultraviolet lights to sanitize its aircraft's cockpits.

As well as cleaning during service, aircraft will have periodic deep cleans. Again, this will vary between airlines and aircraft. SIngapore Airlines reports carrying out deep cleaning every month; British Airways around every 500 flight hours. Deep cleaning will involve all surfaces, seats and fabrics, as well as areas like air vents.

There are many different cleaning methods, strategies, and timings in use with different airlines. Feel free to discuss any that you know more about in the comments.

Journalist - With almost a decade of experience in the publishing sphere, Justin has built up a deep understanding of the issues facing aviation today. With a keen interest in route development, new aircraft, and loyalty, his extensive travels with airlines such as British Airways and Cathay Pacific has given him profound direct comprehension of industry matters. Based in Hong Kong and Darlington, UK.