"In the event of a crash necessitating deployment of the driver-side frontal airbag, the inflator could rupture with metal fragments striking and potentially seriously injuring the vehicle occupants," NHTSA said in its summary of the expanded recall.
Honda said a total of approximately 5.5 million vehicles will be covered by its Takata-related recalls.
Honda dealers will replace the driver-side frontal airbag inflator in all of the affected vehicles. A date has not been set for the expanded recall. Owners can contact Honda customer service at 1-800-999-1009.
Honda said "letters will be sent to registered owners over time, prioritized by geographic area in the order of highest perceived risk."
"Past ruptures have killed or injured vehicle occupants," the company said in a statement on Thursday.
Edmunds says: Owners of these cars should stay in touch with their dealers, especially if they are seeking a loaner car or rental car as they wait for parts to become available.