Egypt Air loses another aircraft

[abaris]

The plane appearently made a complete 360 degree turn before crashing.

That can be attributed either to mechanical or electronic fault, or physical damage to the aircraft that destroyed directional control but left the airframe moderately airworthy otherwise.

Exactly. Right from the start, the spoke of a 90 degree turn followed by doing a 360, while losing height. It wasn't a sudden event like a bomb tearing the fuselage apart. Might still be a bomb, but there's an abundance of other possible reasons too.