¿Aduanas?

They are phasing out customs declarations & the red light/green light system that was in place for many years. My friends who recently visited down here didn't even get the FMM "tourist cards" in Cancun anymore. This new system isn't in place everywhere yet, not even in all terminals in the big airports. Maybe that's why some don't have to bother with customs in Mexico City and others still do. In Cancun it still depends on what terminal you fly into. And the budget airlines (like Interjet mentioned in the parent post) still go to the old terminals.