93. Which FCC license meets the requirements to perform or supervise the performance of at-sea adjustments, servicing, or maintenance which may affect the proper operation of the GMDSS station?

The GMDSS Operator's/Maintainer's license or GMDSS Maintainer's license is required to perform or supervise at-sea maintenance affecting GMDSS station operation, as this license authorizes the necessary technical maintenance authority not provided by operator licenses or general marine radio credentials.