Spirit Airlines said on Thursday it has begun canceling some flights as a strike deadline approaches this weekend.
Also, a check by The Associated Press showed that Spirit is not selling tickets for any flights on Saturday or Sunday. It wasn't clear what Spirit's plans were for passengers who had previously bought tickets to fly those days.
Spirit pilots could walk off the job as soon as 12:01 a.m. Saturday if they don't make a deal in their negotiations with the airline.
Spirit spokeswoman Misty Pinson said the airline canceled some flights in an effort to protect customers from the impact of a strike. She would not provide details. She said the airline is offering travel alternatives to customers.
The airline based in Miramar, Fla., was negotiating in Washington with pilots represented by the Air Line Pilots Association. Both sides have said they would rather make a deal, and strike threats are a common feature of the endgame of airline negotiations. Still, a Spirit strike could disrupt the travel plans for thousands of passengers this weekend.
Spirit has said it plans to keep flying if the pilots walk out. On Wednesday, Pinson said it had lined up air carrier partners to keep flying.
However, pilots have seen no sign of preparations to keep flying, and many management pilots have promised not to cross the picket line, said Sean Creed, a Spirit captain and the head of its union.
Spirit operates about 150 flights a day, generally from the Eastern U.S. to Latin America. That compares to more than 6,200 for Delta Air Lines Inc., the world's biggest carrier by traffic.
Spirit's weekend plans remained a mystery. Its Web site showed no seats for sale on any of its flights for Saturday or Sunday. A reservations agent told the AP that all weekend flights out of its main hub at Fort Lauderdale had been "suspended."
Creed said it appeared that Spirit was canceling flights scheduled around the time of the midnight deadline, based on scheduling notices received by pilots.
Pinson, the company spokeswoman, did not respond to requests for comment about the airline's weekend plans.
Spirit, which is privately held, dubs itself an ultra low-cost carrier. It attracted notice recently when it announced that beginning Aug. 1 it would charge passengers up to $45 for carry-on bags.