NEW YORK (Reuters) - Unions for flight attendants and pilots working for Spirit Airlines are warning members of further pain during the budget carrier's second bankruptcy in a year, as it steps up cost-cutting efforts, according to memos seen by Reuters.

The Florida-based ultra-low-cost airline filed for bankruptcy protection in August for the second time in a year after a previous restructuring did not resolve the carrier's challenges, the company said. 

"This bankruptcy will be much more difficult than the last one and we must be prepared to act to protect our interests," the Association of Flight Attendants said in a Wednesday memo seen by Reuters.

That followed an earlier memo to aviators that said Spirit wants to cut $100 million in annual spending on pilots to conserve cash after previously saying it would furlough about 300 pilots by early November. The carrier plans to cut November flight capacity by 25%, adding that efforts to reduce its cash burn would "inevitably affect" the size of its workforce.

Spirit has asked to meet with the Air Line Pilots Association (ALPA) union leadership to identify cost savings, a spokesperson said in a statement, with a deal expected by Oct. 1.

Spirit faces mounting pressure from creditors, including jetmaker Airbus, which said Spirit owes more than $1 million for parts received, according to filings. Spirit is also in a dispute with aircraft lessor AerCap Holdings ( AER ) over a deal covering 36 Airbus planes due for delivery between 2027 and 2028. 

Jason Ambrosi, president of ALPA, which represents the Spirit pilots, said recently he expects more pilots to be furloughed at a time when the post-COVID travel boom has waned. 

"We now find ourselves in a bit of an oversupply in the U.S., so it's going to be kind of tough to find a landing spot for each one," Ambrosi said.

The 12 major U.S. carriers hired 4,834 pilots last year, down from 13,357 in 2022, according to consultant Kit Darby. 

(Doyinsola Oladipo in New York and Allison Lampert in Montreal; Editing by Aurora Ellis)