A, B, C and D checks
Also: C check, D check, heavy maintenance visit, letter checks
Packages of scheduled maintenance, rising in depth from A to D, that an aircraft undergoes at set intervals of flight hours, cycles or calendar time.
What it is
Beyond daily and transit checks, an airliner's scheduled maintenance is grouped into checks known by letters. An A check comes round every few hundred flight hours, usually fits into a night in the hangar and covers general inspections and routine tasks. The intermediate B check has been folded into the A check in many modern programmes.
A C check goes much deeper. It falls due roughly every one to three years depending on the type, opens up panels to inspect structure and systems, and keeps the aircraft on the ground for one or more weeks. The D check, or heavy maintenance visit, comes round every six to twelve years or so: the aircraft is stripped almost bare, with the interior and sometimes the paint removed, and may spend a month or two in the hangar.
Exact intervals are set by each operator's approved maintenance programme, based on the manufacturer's recommendations, and airlines often use heavy checks to refit cabins.
Related terms
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This page was last updated on October 9, 2026
APA
Vuelopedia. (2026, October 9). A, B, C and D checks. Retrieved October 16, 2026, from https://vuelopedia.org/en/glossary/a-b-c-and-d-checks
MLA
“A, B, C and D checks.” Vuelopedia, Fundación Poderia, 9 Oct. 2026, vuelopedia.org/en/glossary/a-b-c-and-d-checks. Accessed 16 Oct. 2026.
Chicago
Vuelopedia. “A, B, C and D checks.” Fundación Poderia. Last modified October 9, 2026. https://vuelopedia.org/en/glossary/a-b-c-and-d-checks.
Harvard
Vuelopedia (2026) A, B, C and D checks. Available at: https://vuelopedia.org/en/glossary/a-b-c-and-d-checks (Accessed: 16 October 2026).
BibTeX
@misc{vuelopedia_en_glossary_a_b_c_and_d_checks,
author = {{Vuelopedia}},
title = {{A, B, C and D checks}},
publisher = {Fundación Poderia},
year = {2026},
date = {2026-10-09},
url = {https://vuelopedia.org/en/glossary/a-b-c-and-d-checks},
howpublished = {\url{https://vuelopedia.org/en/glossary/a-b-c-and-d-checks}},
urldate = {2026-10-16},
note = {Accessed 2026-10-16}
}Wikipedia
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