Today only! Alaska Airlines is having a flash sale valid for purchase through 11:59pm PT, tonight, April 10. Travel is available through mid-June.
Most routes are valid for travel on Tuesdays, Wednesdays, and Saturdays, from May 1 through June 13. The sale is advertised on their site for travel through May 23, but I'm finding most routes have availability for travel through mid-June. International and Hawaiian routes have more days/week available. Other airlines may be matching prices.