The Seattle-based airline says the New Orleans and Tampa flights start in June and the Detroit flights in September.
The airline says the additions strengthen its route network.
Introductory fares for the new flights start at $149 one-way. Tickets must be purchased by Feb. 26 and travel completed between June 12 and Nov. 19 for Seattle-New Orleans flights, between June 20 and Nov. 10 for Seattle-Tampa, and between Sept. 4 and Nov. 19, 2014, for Seattle-Detroit.
For complete fare rules, including blackout dates and advance purchase requirements, visit www.alaskaair.com or call 1-800-ALASKAAIR (1-800-252-7522).