ADO buses beat domestic flights on most routes

Mexico's first-class bus companies (ADO in the south and east, ETN and Primera Plus in the center and west) run comfortable, air-conditioned coaches with reserved seats and luggage checks, often overnight. Mexico City–Oaxaca or Cancún–Mérida by bus costs a fraction of flying once you count airport transfers. Buy tickets on each company's site or at the terminal, and keep your luggage tag; it's checked on arrival.