Check on our Facebook page where we post details. If we have any special offers, they're usually posted the evening before, or sometimes on the same day as the flights. These tickets are for the returning leg of a trip that's been booked for another customer - i.e. someone's booked a flight from Cancún to Holbox, so there's an empty plane flying back from Holbox. This means that if the customer cancels or changes their flights, your cheap last minute ticket is going to be affected too.
However, these tickets are very popular! They work well for people without a connecting flight or people working on a very flexible schedule.