Spirit Airlines is set to cut jobs as the airline plans to reduce capacity by 25% year-on-year in November, according to a memo, deepening woes for the low-budget carrier.

The cut by the airlines aims to "optimize our network to focus on our strongest markets," CEO Dave Davis told employees in the memo.

"These evaluations will inevitably affect the size of our teams as we become a more efficient airline," the memo said. The number of roles that could be impacted remains unclear.

The low-cost carrier continues to evaluate the size of its fleet and plans to meet with the airlines' union leaders in the coming weeks, according to the memo seen by Reuters on Wednesday.

CNBC earlier reported the restructuring plan.

Spirit filed for bankruptcy protection last month for the second time in a year after a previous reorganization failed to put it on a firmer financial footing.

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Spirit's financial struggles, as well as a rush among U.S. carriers to chase premium travelers, have raised concerns that the era of cheap flights might be over for price-conscious travelers.

Earlier on Tuesday, United Airlines ruled out bidding for assets of Spirit if they become available, which is expected as part of the discount carrier's restructuring process.