Talks were extended past a midnight deadline, but the pilots announced the walkout on a hot line message at 5:30 a.m. EDT. The company confirmed the strike and announced it was canceling its Saturday flights on its website.
A spokeswoman for the airline did not immediately return a call seeking comment.
Spirit pilots have said their pay lags that of competitors.
Privately-held Spirit runs roughly 150 flights a day, making it much smaller than major carriers like Delta. Still, the walkout and cancellations were likely to affect thousands of travelers.
The airline is based in Miramar, Fla.
