I think you also can't overlook the merits of EZE as a destination for business travel relative to the many other cities that UA flies to long haul. Far fewer business travelers are headed to EZE than GRU or MEX for example, not to mention LHR, HKG, FRA, etc etc. The business climate in EZE is simply much more complicated and that has frightened off many who would invest or conduct business there. (I say this as someone in charge of sales for a company that DOES do business in EZE -- just being realistic in stating that it's not everyone's cup of tea.) Still, EZE's popularity as a tourism destination has grown tremendously since the 2002 devaluation, naturally giving you more Y fares and mileage redemptions.

If the FT consensus is that C and F fares bought by business travelers play a significant part in making a route profitable (along with cargo and other considerations), it would follow that UA is likely not selling as many C and F fares to EZE as they are to other destinations which see more service.

In my case, I could push my company to pay for C when I go to EZE, but I don't since I would exhaust my yearly travel budget after 2-3 trips. I also don't push for it since as a 1K or 1P every year, I'm virtually guaranteed an exit row or E+ seating. Then there are some flights like the one I took two weeks ago EZE-IAD, when I get op up'd -- which should tell you that Y is oversold, but C had availability.

These are all likely reasons why UA in particular needs to keep Y fares high on this route. I don't think there are outside regulatory factors or cartel-like behavior involved. Especially since I remember the good old days in 2002-03 when I grabbed some E-Savers IAD-EZE for $450 round trip - all in!

You also can't forget the loyal Argentines and Uruguayans who built up miles in the MP program back when UA had more service to EZE and MVD. They still compete with gringos for what few free seats UA opens up.