What regulation prohibits the operation of an aircraft that has undergone alterations affecting its flight characteristics until checked by an appropriately-rated pilot?

The regulation that prohibits the operation of an aircraft that has undergone alterations affecting its flight characteristics until checked by an appropriately-rated pilot is 14 CFR 91.407. This regulation specifically addresses maintenance and alterations to aircraft, stating that after an aircraft has been altered in a way that affects its operational capacity or flight characteristics, it must not be flown until it has been tested and inspected by an appropriately-rated pilot to ensure that it is safe to operate.

This requirement is crucial for maintaining aviation safety, as alterations can significantly impact how an aircraft handles during flight. The regulation underscores the need for a thorough evaluation by a qualified individual who possesses the knowledge and expertise to assess the changes made to the aircraft.

In contrast, the other options pertain to different aspects of aircraft operation and maintenance. For instance, 14 CFR 91.405 deals with the responsibility of the owner or operator to maintain an aircraft in an airworthy condition, while 14 CFR 21.190 concerns the issuance of amended type certificates. Lastly, 14 CFR 65.107 relates to the certification requirements for repairmen, not the operational standards for altered aircraft.