Definition
A scheduled heavy maintenance inspection performed on transport-category aircraft at intervals defined by the manufacturer's maintenance program, typically every 20 to 24 months or after a specified number of flight hours. A C-Check requires the aircraft to be taken out of service and moved into a hangar, where most of its systems and components are inspected, tested, and serviced in detail. It is more extensive than the routine A-Check and B-Check but less comprehensive than the structural D-Check.
Plain English
A major scheduled inspection of an airliner that takes the aircraft out of service for one to two weeks, during which most systems are checked thoroughly in a hangar.
Context Anchor
Seen in airline maintenance planning, aircraft logbook discussions, maintenance schedules, and conversations about why an aircraft is temporarily out of service.
Derivation
The letter checks (A, B, C, D) were introduced by airline maintenance programs to label inspections by increasing depth and interval. C is the third level — deeper than A and B, but not as extensive as the airframe-heavy D-Check.
Why Pilots Care
Confirms the aircraft meets all airworthiness requirements before returning to flight operations.
Intuition Check
Do not confuse a C-Check with a pilot’s quick preflight check. A C-Check is a planned maintenance event performed by maintenance personnel, not a cockpit checklist item.
Example Sentence 1
The aircraft was ferried to the maintenance base for its scheduled C-Check before returning to revenue service.
Example Sentence 2
Technicians completed the C-Check and signed off all required work before the next flight.