if he plans on doing this during the Winter months. Id suggest he take a Detour and go via the I-10. As its been known that Blizzards happen and does Close and makes lousy driving Conditions in both New Mexico and Arizona. Ive got stuck twice.

Its not really out of his way as by Flagstaff,Az he will have to take the I-17 south to PHX anyway. Which takes me under 2 hrs and I drive with a HEAVY Foot. So Im sure it'll be more like 3 - 3+ hrs for your father.