UFOs that swarmed over a fleet of Navy warships almost three years ago remains unexplained.In close encounters that lasted for hours, the mystery crafts, complete with multi-coloured flashing lights, repeatedly appeared over vessels off the southern California coast during July 2019.Navy chiefs initially reported they were reasonably confident that the UFOs were drones. READ MORE: 'Third-world jail' where Maxwell will live alongside rapists, murderers and terroristsBut documentary filmmaker Jeremy Corbell has said the ships’ crews claim the craft possessed capabilities beyond traditional human vehicles.