Plane engine falls apart mid-flight from San Francisco to Honolulu

Every plane passenger's nightmare has come to life after the engine of a passenger plane flying from San Francisco to Honolulu broke apart mid-flight.

In a terrifying equipment malfunction, the outer shell of the engine on United Airlines flight UA1175 fell off and left the inner workings exposed to the elements while thousands of metres in the air.

Several passengers on the plane posted pictures of the drama to Twitter, with a video uploaded by Erik Haddad garnering more than 184,000 views in just a few hours.

It is not known how the engine fell apart, with authorities expected to investigate the plane.