You can fly internationally between Sucre and Buenos Aires, Madrid, Salta and São Paulo on BoA.
BoA, Ecojet and Amaszonas offer several flights a day to Cochabamba, La Paz and Santa Cruz; Amaszonas also flies to Uyuni (around B$374 one way) daily Monday, Wednesday and Friday. There are direct flights on BoA to Tarija several days a week. TAM also serves Sucre, La Paz and Santa Cruz, however, the location of its local office was in flux when we last visited.
The city's new airport named Alcantarí International Airport, located in Yamparáez, 30km south of the city, is still a work in progress. The space feels mostly vacant, with few shops or eateries open, especially for night flights. There is an ATM, but no money exchange. Unlike the old airport, however, it's less vulnerable to bad weather and certainly isn't in danger of being overrun by housing developments. Departure tax is B$11.
The airport is a 40-minute taxi ride (B$50) from the city at night (longer during the day when there's more traffic). Or you can grab a shared one, minimum two people (B$60), from Plaza Tréveris or a micro that leaves when full from a spot near Plaza Camargo (B$8).