Frontier Airlines is being sued by customers who say the company markets itself as having the lowest fares while adding hidden fees.

The class action lawsuit filed in the U.S. District Court in Middle Florida claims the Denver-based airline’s fares are similar to other airlines’ after all the fees are included and label this as “misleading advertising.” The plaintiff is seeking a refund of the fees and $100 million in punitive damages for themselves and others.

“Frontier makes up whatever discount it purports to give consumers in fraudulent and unwarranted charges,” the lawsuit alleges.

For instance, the lawsuit alleges that a carry-on piece of luggage sometimes costs as much as four times the price for a checked bag, according to the lawsuit. It also says gate attendants for Frontier earned bonuses for charging people additional baggage fees at the gate.

Additionally, the lawsuit says Frontier tells customers they are allowed to bring one free personal item on the plane, but uses a measuring instrument at the gate that is smaller than the dimensions advertised. Moreover, the lawsuit alleges the airline doesn’t adequately disclose the fee for oversized bags, especially when flights are booked through a third-party vendor.

The plaintiffs say Frontier’s actions constitute fraud and violate Florida’s Deceptive Trade Practices Act and Consumer Protections Act. A spokesperson for Frontier said the airline doesn’t comment on pending litigation.

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