What is the Mystery of the Bermuda Triangle?

The Disappearance of Flight 19 1 of 9

It's common for single planes to get lost or go down in the Bermuda Triangle, but the disappearance of Flight 19 stands out because it actually involved five different planes. On December 5, 1945, five naval planes went on a training flight in the Bermuda Triangle and were never seen again.

The current report reads that the disappearance was attributed to "causes or reasons unknown."