Probably some combination of all the above. Many people don't realize just how much further east South America is from the United States. For example, if you go due south from where I currently am in the vicinity of RDU you end up right around Quito, Ecuador not far from the Pacific Ocean. My dad once decided to save $50/person flying our family to GRU via DFW instead of MIA, on this flight it added almost 2.5 hours because we started so much further west.