Originally Posted by
andreadbc
The Base fare is not necessarily sold out for those dates, it may not be showing up because there's a minimum stay or Saturday night requirement or something like that. Try checking out the departure date with a new return date a couple of weeks away and viceversa for the return date and you should be able to see if the Base fare is sold out or not (if it is, it should say "Agotado").
I guess it doesn't really matter because I can't book the Base fare anyway. As long as I am safe to do so and not required to pay additional fees/fines then I will book the "Base Plus" fare.