Definition
A change to an aircraft, engine, propeller, or appliance that does not appreciably affect weight, balance, structural strength, performance, powerplant operation, flight characteristics, or other qualities affecting airworthiness. Anything that does not meet the FAA's definition of a major alteration is classified as a minor alteration, and it can typically be approved and recorded by an appropriately rated mechanic without requiring FAA field approval or an STC.
Plain English
A small change to the aircraft that doesn't meaningfully affect how it flies, how strong it is, or how safely it operates. Because the change is small, the paperwork and approval process is much simpler than for a major change.
Context Anchor
Seen when discussing installation of equipment such as an angle of attack indicator, where the change may be handled as a minor alteration if it meets FAA requirements.
Derivation
Minor comes from Latin meaning “smaller” or “lesser.” Alteration comes from a word meaning “to make different.” In this aviation use, “minor” does not mean casual or unimportant; it means the change falls into the lesser regulatory category.
Why Pilots Care
The classification matters because it determines what paperwork is required and who can sign off on the work. A minor alteration can usually be logged with a standard logbook entry, while a major alteration requires a Form 337 and FAA approval. Pilots reviewing aircraft records need to recognize whether prior modifications were properly classified and documented.
Intuition Check
Do not read “minor” as “anyone can do it” or “paperwork does not matter.” Here, “minor” means the change is not considered a major alteration under FAA maintenance rules.
Example Sentence 1
Installing the new angle of attack indicator was treated as a minor alteration and recorded with a standard logbook entry by the shop.
Example Sentence 2
Because the new instrument qualified as a minor alteration, the owner avoided the need for a supplemental type certificate.