Upon unsuccessful selection of the City Pair flight, what action is required by the traveler according to regulations?

When a traveler is unsuccessful in securing a City Pair flight, they are required to provide written justification and a reason code. This action is mandated by the regulations to ensure transparency and accountability in travel decision-making. The justification helps document why the traveler could not use the City Pair option, which is typically a more cost-effective fare provided by the government. By requiring this written explanation, the system ensures that the travel process adheres to the necessary protocols and allows for proper tracking of travel choices. The reason code serves as a categorical explanation to streamline and standardize the justification process across the board.

Other actions like canceling the trip and rebooking, choosing another flight immediately, or consulting the travel office, while could be valid responses in different contexts, do not align with the specific regulation that mandates the written justification after failing to secure the City Pair flight.