How planes are checked

Before every flight

Before departure, the aircraft gets a walkaround inspection and its technical log is reviewed. Anything reported on earlier flights is either fixed or handled under strict, regulator-approved rules that say exactly what may wait and for how long.

The lettered checks

On top of the daily work, airlines have traditionally grouped inspections into checks named by letter. Typical intervals:

• A check: about every 400 to 600 flight hours (roughly 200 to 300 flights), usually overnight.
• B check: on modern aircraft no longer a separate visit; its tasks are folded into the A checks.
• C check: about every 20 to 24 months, with the aircraft out of service for one to four weeks while its structure and systems are inspected in detail.
• D check, or heavy maintenance visit: about every 6 to 10 years. The aircraft is largely taken apart, down to the bare structure, and inspected for fatigue and corrosion.

These are typical ranges, not rules. Each airline runs its own maintenance program, approved by its regulator, that sets every task by flight hours, number of flights, or calendar time. Newer jets such as the 787 and A350 schedule individual tasks rather than fixed letter checks, but the idea is the same: everything is inspected, on a clock.

Why a crack is found early

Modern airframes are designed on the assumption that small cracks will eventually appear. Inspections are spaced so that a crack is visible at several checks in a row while it is still far too small to matter, which gives the system many chances to catch it. Manufacturers also run full-scale fatigue tests far beyond a type's design life: Boeing ran its 787 test article to about 165,000 flights, nearly four lifetimes.

Fix orders and defect reports

When a problem turns up anywhere in a fleet, the regulator can issue an airworthiness directive, a legally binding order to inspect or fix specific aircraft by a deadline. In the United States, airlines must also report serious problems found during maintenance to the FAA. This site reads those directives and the FAA's defect reports every week.

Who checks the checkers

Airline maintenance programs are approved and audited by regulators. And because the same aircraft type is flown by dozens of airlines answering to different regulators on several continents, a hidden problem would have to escape all of them at once. That independence is why a quiet record across a whole fleet means something.

What this site can and cannot show

We show inspection orders, accident records, fleet ages and, where they exist, the FAA's defect reports. We do not have any specific plane's check history: airlines share those records with their regulators, not with the public, so we never display a "last checked" date we cannot source.