I believe he explained his actions by uttering “Allahu Akhbar” a few times as the plane spiraled in.
There was a lot of wrangling and arguing between the various government agencies as well as with the foreign investigators over the meaning, context and translation of “Twakalt ala Allah” - “I rely on God”
Here's what I think happened. Several Orthodox Jews were known to have been on the flight. My guess is that Batouti was seated near them and became aware of them. Then all that good Religion of Peace Teaching kicked in, he went up to the cockpit, pulled rank, and killed the infidels in the glorious name of Allah.