Frontier Airlines filed for bankruptcy protection but plans to maintain normal operations

. The bankruptcy followed a decision by the carrier's credit card processor "to start withholding significant proceeds received from the sale of Frontier tickets," according to CEO Sean Menke. "To be clear, we filed for very different reasons than those of other recent carriers." According to a research note from JP Morgan Securities analysts, "Given Frontier's sensitive liquidity position, we believe its processor was already withholding as much as 50 percent of sale proceeds until time of flight, and may have boosted that to 100 percent in recent weeks."