Absence seizures don't really work like that, and they don't really show up as a new diagnosis in someone that age. A prior diagnosis would have disqualified him from getting a commercial (and probably a private) pilot's license. And automatisms won't don't that. My wife is an epileptologist, I know far more than I want to about these things.
They might not work like that when the condition causing them is Epilepsy, which I agree isn't really a thing that just randomly happens.
That said, there still could be some kind of neurological condition behind this, I am not a doctor so I am not going to argue the specific diagnosis, I'm sure your wife is right.
The thing that makes me think there was something physically wrong (be it drugs or pathology), is the fact he is reported as "breathing normally" during the whole thing, even if he was a terrorist or suicidal, he would still have the fight or flight reaction, and there is no way rapidly approaching a cliff wall and knowing you are going to die and kill 200 (or however many) people in the process would not trigger the fight or fight response, and one of the main symptoms of a big adrenaline surge is an increase in breathing and heart rate.