C Check — C Check — Aircraft Maintenance

C Check

The C Check is the primary heavy maintenance event in most commercial aircraft programmes. It represents the transition from line maintenance to base maintenance — the aircraft is inducted into a hangar, potentially stripped of furnishings and panels, and subjected to the most thorough inspection since the previous C Check.

C Check Scope

A C Check workscope typically includes: detailed structural inspection of fuselage, wings, empennage and landing gear bays, inspection and functional testing of all major systems (hydraulic, pneumatic, fuel, electrical, flight controls, avionics), overhaul or replacement of components reaching their life limits, cabin strip-down and refurbishment (if scheduled), corrosion treatment, complete inspection of the aircraft's technical records and deferred defect backlog clearance.

Interval Variability

C Check intervals are aircraft-type and AMP-specific. The 20–24 month or 6,000 flight hour figure is a general approximation. Modern widebody aircraft (A350, B787) may have extended C Check intervals of 6–8 years thanks to composite structures and continuous health monitoring, while older narrow-body types typically conform more closely to the traditional interval.

C Check Economics

A C Check typically costs $1–3 million depending on aircraft type, workscope and labour rates at the MRO facility. Airlines plan C Checks years in advance, often timing them with cabin refurbishment projects to maximise the revenue value of the downtime.

Out-of-Phase Items

Not all C Check tasks occur at every C Check visit. Some items have intervals of 2C, 4C or specific calendar/hour thresholds, creating a layered workscope that grows with each successive check visit.