Family on flight, been watching all day. Why does the flight path swing north to San Diego and east to Dallas instead of the direct path over Mexico?
Just a swag, but it may be weather related. Assuming it was Qantas 7 QF7 from SYD-DFW, other flights were more direct.
Satellite shots from weather.gov showed some weather over Mexico, so they just may have gone around.
(disclaimer- no expertise, just observing)