Playlist
A look at the events leading up to the crash of flight JAL123, which killed 520 people - the deadliest single-aircraft accident in history.
A Martinair flight crashes in Portugal amid thunderstorms, and when investigators gather the evidence the mystery only deepens.
Easter Island's tall stone moai have long captured the global imagination, and there are still mysteries surrounding them.
Former radar specialists, pilots and security guards at Area 51 cast new light on the secretive and ground-breaking research conducted at the Groom Lake Testing Facility. 7+.