Definition
An FAA Aviation Safety Inspector assigned by the Flight Standards District Office (FSDO) as the primary point of oversight for the maintenance program of a specific air carrier or repair station. The Principal Maintenance Inspector (PMI) reviews and approves maintenance manuals, training programs, and inspection procedures, and monitors ongoing compliance with the Federal Aviation Regulations.
Plain English
The FAA inspector who is personally responsible for keeping an eye on how a particular airline or repair shop maintains its aircraft. They approve the company's maintenance procedures and check that the work is being done correctly and legally.
Context Anchor
You may see this term in discussions of FAA oversight, airline maintenance programs, repair station inspections, or official maintenance findings.
Derivation
Principal' here means 'main' or 'lead' — the senior inspector with primary responsibility — rather than the everyday school-related sense of the word.
Why Pilots Care
For pilots flying for an airline or charter operator, the PMI is the FAA official whose approvals shape the maintenance program their aircraft operate under. Changes to inspection intervals, manuals, or procedures usually require PMI sign-off.
Intuition Check
Principal does not mean a school principal here. It means the primary or main inspector assigned to maintenance oversight for that organization.
Example Sentence 1
The airline submitted its revised maintenance manual to the Principal Maintenance Inspector for approval before the new inspection program could take effect.
Example Sentence 2
Any changes to the approved maintenance program must be coordinated through the assigned Principal Maintenance Inspector.