
Continuity mistake: When John and Catherine are in the hangar at the runway, the Cessna's tail number is N3035C. When the plane is shown in the air, the number is N3973F. When they land, the tail number has changed back to N3035C. (01:22:25 - 01:25:50)
Answer: He didn't program the Terminator, she did - remember, John is dead, successfully eliminated by that very Terminator. As to why she didn't program the Terminator to obey both of them, that's an open question - possibly she needed to supply a voiceprint which obviously couldn't be obtained from the deceased John (which would also explain why the Terminator in T2 appeared to only be programmed to obey John, not both John and his mother). Alternatively, it's plausible that the Terminators can only be programmed to obey one individual, in order to prevent problems in the case of conflicting orders.
Tailkinker ★