Passengers on a United Airlines flight to Hawaii have described hearing a "bang" before the plane started "really started shaking", with one calling it the "scariest flight of my life".
Flight 1175, which was travelling to Honolulu from San Francisco, landed safely on Tuesday in Hawaii after an engine cover came off during its flight from California, the airline said.
"Our pilots followed all necessary protocols to safely land the aircraft," United said in a statement, adding that all passengers departed the Boeing 777 normally at the gate.
The airliner landed as emergency responders waited nearby, said Hawaii Department of Transportation spokesman Tim Sakahara.
Images posted on social media show an engine with the exterior cover missing as the plane approaches Honolulu. Video shows the engine shaking back and forth with pieces of the cover flapping in the wind.
"There was a loud bang ... and then the plane really started shaking," passenger Allison Sudiacal told Hawaii News Now.
"There was a loud boom and then it was like rattling and the plane was kind of shaking like boom, boom, boom."
Sudiacal was travelling with her four-month-old son, her husband, Tim, and his parents.
"They let us know that we had to brace for impact in case there was a rough landing. It was scary. But they did a really good job," Sudiacal said.
Erik Haddad, a Google engineer on board the flight, posted a picture of the exposed engine on Twitter, joking: “I don’t see anything about this in the manual.”
Another passenger, Maria Falaschi, described it as the “scariest flight of my life”.
"You could tell everyone was scared, but the crew and pilots did a great job," she added.
Passenger Haley Ebert told the New York Times she heard a “huge bam” as part of the casing came away from the engine.
“Everyone on our side flung open their windows just to see what it was,” Ms Ebert said.
“The casing to the engine had sort of flown off. There were pieces flying into the ocean, nuts and bolts flying out a little bit. A bolt hit the wing, and it just made this huge bam.”
An emergency was declared due to a vibration in the right engine, said Federal Aviation Administration spokesman Ian Gregor said in an email, adding that the agency will investigate the incident.