SilkAir had 2 up front.
I don't believe that's been established for certain, as there was a period of from 5 to 10 minutes from the time the CVR stopped recording before the aircraft went into a death dive. Authorities have speculated that during that time (after Capt. Tsu returned to the cockpit and pulled the breaker), FO Ward may have left the flight deck for whatever reason.
I seem to recall the crash of Air France 422 (actually operated by TAME) in 1998 was for a time suspected as suicide as the normal takeoff procedures from Bogota appeared to have been disregarded before it flew into a mountain. It occurred not long after SilkAir, which may have fueled some of the suspicions. In any case, the probable cause was eventually listed as loss of situational awareness in crap weather.