The sight of an engine covering ripping off a plane mid-flight shocked passengers travelling from San Francisco to Honolulu.
United Airlines Flight 1175 was eventually forced to make an emergency landing but no injuries were reported.
A video of the exposed jet engine shaking mid-flight was shared to Twitter by passenger Erik Haddad.
United Airlines released a statement after the plane landed but did not say what the cause of the problem was.
"United flight 1175 travelling to Honolulu from San Francisco landed safely after the pilots called for an emergency landing because of a loss of the engine cowling (the covering of the engine)," the statement read.
"Our pilots followed all necessary protocols to safely land the aircraft.
"The aircraft taxied to the gate and passengers deplaned normally."
