Technical Order 00-20-1 Aerospace Equipment Maintenance Inspection, Documentation, Policies, And Procedures

Maintenance symbols are a quick way to convey the status of equipment so a technician knows what action is needed just by looking at the symbol. When the symbol is a red dash, it signals that the current condition of the equipment is unknown. That uncertainty matters because it means there could be a latent or more serious defect that isn’t evident from a quick check. In practice, this prompts additional diagnostics, tests, or inspections to determine safety and operability before deciding on further action. The red dash thus flags the highest level of caution: don’t assume the part is OK or clearly bad—investigate further to uncover the true condition. Other marks convey different established statuses, such as known unserviceable or already addressed conditions, which do not communicate that ambiguity and potential hidden risk.