The cleaning service functions similarly to the catering service, but the opposite way around. Cleaning trucks will bring trash from planes to a depot. Then, other trucks will take the trash away.
After deboarding is complete, a cleaning truck picks up trash from the medium or large aircraft. Then, when the truck fills up (normally after a few flights) the truck will unload the trash into a garbage depot. This deport will fill up, and when full, it will request a pickup. Then, waste hailers from the outside world will pick up and bring away trash.
Important note: Cleaning will only take place after deboarding has finished and boarding will only start when cleaning is finished!