Green means proven.

A system must never assert a compliant status derived from data it failed to retrieve. If a lookup, query or calculation did not complete, the status it feeds must read as not evaluated.

A failed request and a clean aircraft produce identical screens if the failure is swallowed. The operator cannot tell a healthy fleet from a broken connection, and the empty state — "nothing due" — reads as reassurance.

When importing status from an external record, any verdict the system cannot positively recognise must be recorded as unknown. The fallback bucket must never be the compliant one.

Source reports carry verdicts that vary by provider and by decade. A default of "complied" silently converts everything unfamiliar into satisfied — including the verdicts that mean the exact opposite, which are the ones that matter most.

Remaining life on a life-limited or hard-time item must be computed only from a recorded starting point. Where time at installation was never captured, the item must read as needing an initial record, not as within limit.

Assuming a zero-time install is wrong in the unsafe direction. A part that went on used can sit at or past its limit while the sheet prints a confident figure for cycles remaining.

An aircraft or fleet with no established maintenance baseline must never report as clear, airworthy or ready to dispatch. Nothing established is a distinct state from nothing due.

The two look the same in every summary count that starts at zero. A tail nobody has loaded yet reports the same clean numbers as a tail that is genuinely current.

Where an interval, unit or limit cannot be interpreted, the item must surface for human review. It must not fall through to a default status.

Programs use units that vary by manufacturer and by era — daily, annual, landings, cycles, calendar months, operating hours. Any one the logic does not handle takes the default branch, and the default is usually green.