Flight path Question

Why would a jetliner fly away from its destination with only 100 miles to go? See flight path compared with planned flight path.

flightaware.com/live/flight/SWA5 … /KLAS/KSMF

Most Class B airports have predefined arrivals that airliners follow. This flight just had to do a little manuevaring to join that arrival, in this case the FLUNK3 arrival (note the text in the route box).

This one flew so far south that it joined the CZQ arrival plan.