Progressive Inspections (FAR 91.409)
To minimize maintenance downtime, owners may opt for a progressive inspection plan. Progressive inspections benefit owners whose aircraft experience high usage such as FBOs, flight schools, and corporate flight departments.
Unlike an annual or 100-hour inspection, a progressive inspection allows for more frequent but shorter inspection phases, as long as all items required for the annual and 100-hour are inspected within the required time.
Example: Flight schools with aircraft that must comply with the 100-hour inspection normally use four inspection phases at 25-hour intervals. The inspection cycle is completed when the last inspection is endorsed.
The authority to use a progressive inspection plan is non-transferable. Once the aircraft is sold, an annual (or if applicable, a 100-hour) inspection must be endorsed within 12 calendar months (or 100 hours) of the last complete cycle.
Most airframe manufacturers will provide a boilerplate progressive maintenance plan.