Final answer:
When an aircraft is out of service or will remain idle for a certain number of days, maintenance will put the aircraft in Level I preservation.
Step-by-step explanation:
In the aviation industry, when an aircraft is out of service or will remain idle for a certain number of days, maintenance will put the aircraft in Level I preservation. Level I preservation involves certain procedures and actions to protect the aircraft from deteriorating during its idle period. The specific number of days required for Level I preservation may vary depending on the aircraft type and maintenance policies of the airline or organization.