You can pause your company by using the Pause button in the Global Settings:

Your company will not be charged any fees until you return.
Be aware that you will need to stop all aircraft rentals before pausing.
In the past, we archived companies not used for 2 months to avoid negative cash. If you come back and are in this case, start playing with a new company, then open a ticket via zendesk ( https://onairhelp.zendesk.com/ ) with your new company’s 4 digits airline code and we will transfer your company value (including all assets and aircraft values) and your XP/Level back.