United announced it would start up this Saturday only service from DEN to CUN, but I checked to book a tickets and its not for sale. I know United said it was subject to government approval...did it not receive that, change its mind, or am I wrong that seats are for sale on this route?

I am excited that United is growing in the Caribbean/Central America, (as well as its route map) and hope that this route is indeed operating. Anyone have any answers?