On the surface, Helios Airways flight 522 seems ominous, as if it had been done on purpose. Why else would oxygen masks have been deployed with no move to descend to a breathable altitude? Why else ...

A lack of oxygen in the cabin incapacitated Helios Airways Flight 522's crew, and the plane eventually crashed into a mountain after running out of fuel.

The history of aviation has seen many strange and shocking plane crashes but there are few that are as mysterious as the fate of Helios Airways Flight 522. It became known as the "Greek Ghost Flight" ...