[alrea]

My guess is that the stolen passports attempted to hijack the plane and then there was a fight in the cockpit, like flight 93.

Would a black box show whether this happened?

[red-dawg]

The "black box" consists of a flight data recorder and a cockpit voice recorder.

The FDR records specific aircraft performance parameters such as altitude, speed and a host of other functions, so if there was a sudden nosedive it would show it.

The CVR records sounds in the cockpit and radio transmissions.

So, theoretically, yes.