What action should be taken if the air brakes on a car fail en route?

Cutting out the air brakes on a car and notifying the Network Operations Center (NOC) is the appropriate action to take when air brakes fail en route. This procedure is crucial because it allows the train to continue operating safely while ensuring that the failure is promptly reported for further action. Cutting out the air brakes isolates the defective system, minimizing the risk of further issues while the train remains in operation.

Notifying the NOC is equally important, as this allows the responsible personnel to coordinate any necessary adjustments or repairs and provide guidance based on the situation. This ensures that the safety protocols are followed, and the next steps can be appropriately managed.

The other choices would not conform to safety procedures. For instance, proceeding with caution does not adequately address the malfunction, potentially leading to unsafe conditions. Stopping the train and waiting for repair crews may not be feasible depending on the circumstances, and it could disrupt service. Completely removing the car from the train might be excessive if the situation can be handled by isolating the brakes and administrating a proper response through the NOC.