Quito's Aeropuerto Internacional Mariscal Sucre is 37km east of the city in a broad valley near Tababela. It's a modern facility with the longest runway in Latin America and the second-highest control tower (after Cancun); however, the terminal is significantly smaller than Guayaquil's. There is a tourist information booth in the arrivals hall.
Taxi prices into the city are fixed and cost $26 to the Mariscal or Old Town. After exiting customs there's a small kiosk with the rates conveniently posted. Depending on the time of day and traffic, the trip takes between 35 minutes and an hour.
Every half-hour, the Aeroservicios shuttle bus makes the 30-minute trip between the airport and Parque Bicentenario (the old airport) at the northern end of Avenida Amazonas. From here, taxis are cheaper into the Mariscal or Old Town, respectively only 9km or 15km away.
The least expensive and least convenient alternative is to take a public bus ($2) to or from the Río Coca bus terminal north of the Mariscal.