The union and the airline were still working out the details of when pilots would return to flying. Pilots technically remain on strike until that is done, said Andy Nelson, the vice chairman of the council for the Spirit branch of the Air Line Pilots Association.
"Our intention is to help get the airline back up and running as quickly and efficiently as possible," he said. Spirit has canceled all flights through Thursday.
A Spirit spokeswoman did not immediately respond to a phone message seeking comment.
Spirit pilots walked out Saturday morning in a pay dispute, saying they ought to make a wage comparable to their counterparts at other discount airlines like JetBlue Airways Corp. and Airtran Airways.
The strike grounded Spirit, which had said it intended to fly through any job action.
That didn't happen, and many of its customers found themselves stranded with limited ability to use their tickets on other airlines.
Spirit carries roughly 16,000 passengers per day, or about 1 percent of the nation's air traffic. Its biggest hub is in Fort Lauderdale, with flights to U.S. cities including Detroit and Atlantic City, N.J., as well as the Caribbean and Latin America.
Spirit is privately held and based in Miramar, Fla.
Airline strikes are rare in the U.S. because of strict federal rules aimed at keeping the transportation system moving. The last strike at a major carrier was when mechanics struck at Northwest Airlines beginning in 2005.
Spirit pilots had been negotiating for more than three years before the strike started Saturday morning. The main issue was pay. Spirit was offering raises. But pilots said the raises were too small considering they would have to fly more to get the extra money, and that the increases were spread over eight years, counting both the proposed five-year contract and the years leading up to it.
Details of the new agreement weren't immediately available.
