I wonder if the UTA gave any consideration to where the frequent fliers live in this valley before they determined which line would get the extension to the airport. My bet is that most frequent fliers reside east of I-15, and therefore extending the Sandy line would have made more sense than a line that originates in the west side of the valley and goes east and then heads west again to get to the airport.
Why would anyone living on the west board a TRAX train that has to make its way through downtown, when they could go north to the airport? East-siders and south valley residents (where most frequent fliers live) would have a "no change of TRAX trains" if the Sandy line were extended to the airport. Is this too logical?