The short answer
The 100-hour inspection is required when an aircraft is operated for hire — including flight instruction for hire — every 100 hours of time in service. Its scope is identical to an annual inspection, but it may be performed and approved by an A&P mechanic without Inspection Authorization.
When it applies
Privately operated aircraft not flown for hire don't need 100-hour inspections — the annual covers them. The requirement attaches to carrying persons for hire or providing flight instruction for hire, which is why trainers and rental fleets live on the 100-hour cycle.
The 100-hour limit may be exceeded by up to 10 hours to reach a place where the inspection can be done, but the overage counts against the next interval: fly to 105 hours and the next inspection is due at 200, not 205.
Related terms and reading
Keep every hour and inspection straight
Maggneto tracks engine times, inspections, and ADs from your actual logbooks — so terms like these become numbers you can act on. Browse the full maintenance glossary.
Frequently asked questions
Does my privately flown aircraft need 100-hour inspections?
No — if the aircraft isn't operated for hire or used for flight instruction for hire, only the annual inspection applies. Many owners still adopt similar interim checks voluntarily.