A United Airlines flight made an emergency landing yesterday after the protective cowling on one of its engines detached from the plane and fell away.

Terrified passengers on board Flight 1175 from San Francisco to Honolulu reported a loud bang when the incident occurred, followed by severe shaking.

The Federal Aviation Administration (FAA) said the pilot "declared an emergency due to a vibration in the right engine." The flight landed safely on schedule at Daniel K. Inouye International Airport in Honolulu and all passengers disembarked normally. Aircraft rescue and fire crews responded as a precautionary measure. Airport operations were unaffected by the incident.

Video and images posted to social media showed what appeared to be the right engine of a Boeing 777 without its front cowling.

Both the FAA and the National Transportation Safety Board (NTSB) plant to investigate.