Oaxaca has a small international airport (IATA: OAX) about 7 km south of the city centre, with direct flights from Mexico City (45 minutes, multiple daily departures with Aeromexico and others), and some routes from Tijuana, Monterrey, and — seasonally — Houston and Los Angeles. From Mexico City, the ADO bus is a popular alternative: first-class coaches take about 6 hours along a dramatic mountain road over the Sierra Madre, and the buses are comfortable. The second-class bus terminal in Oaxaca serves regional destinations and is used for day trips within the valley.