When should an overdue inspection be signed off?

The correct answer indicates that an overdue inspection should be signed off at the end of the flight when the required inspection time has been exceeded. This approach ensures that the aircraft is maintained in compliance with safety regulations and operational standards. Signing off the inspection at this point signifies that the conditions of the aircraft have been assessed, and any overdue maintenance has been addressed.

End-of-flight sign-offs also prioritize operational safety, as they document the aircraft's condition after use and before the next flight cycle. This helps to maintain an accurate maintenance log and ensures that any discrepancies are noted and resolved before the aircraft is dispatched again.

The other options do not align with safe aviation practices. For instance, signing off overdue inspections after a specific percentage over the required frequency can lead to potential safety hazards, while signing off immediately after the inspection may not take into account potential issues arising during the flight itself. Finally, leaving it to maintenance discretion without a clear policy could create inconsistencies in how inspections are managed across different aircraft or operations.