DENVER (KDVR) – The Colorado Attorney General has sent a letter to the U.S. Department of Transportation asking for an investigation into Frontier Airlines after receiving numerous complaints from consumers who were unable to use airline vouchers after COVID-19 affected their travel plans.

“As Attorney General of Colorado, I strongly urge the U.S. Department of Transportation (“USDOT”) to examine the flight change policies and customer service practices of Frontier Airlines (“Frontier”) during the COVID-19 pandemic,” the letter, from Phil Weiser, the Colorado Attorney General, says.  “I also request that you use your authority under federal law to protect consumers by ordering Frontier to stop any unfair and deceptive practices and, where appropriate, seeking civil penalties.  Since March 2020, my office received and reviewed more than one hundred complaints against Frontier from consumers in Colorado and 29 other states—more than about any other company during that time. Consumer reports indicate Frontier violated the federal protections for aviation consumers that you are authorized to enforce.”

In June, the FOX31 Problem Solvers reported that at least five federal class-action lawsuits had been filed against Frontier Airlines since April, alleging the company failed to provide proper refunds to customers whose travel plans were affected by the COVID-19 pandemic.

>>READ MORE: Colorado AG letter to USDOT regarding Frontier

“Instead of fulfilling its obligations under federal law and honoring its passengers’ contractual rights, Frontier has engaged in a pattern and practice of denying refund payments to its passengers for flights cancelled as a result of the COVID-19 pandemic,” one suit, filed in the name of plaintiff Shirley Johnson, alleged.

A Frontier spokesperson told the FOX31 Problem Solvers the company has complied with all federal regulations.

“Throughout the pandemic, Frontier Airlines has acted in good faith to care for our passengers compassionately and fairly.   At all times we have remained in full compliance with DOT rules and regulations governing flight changes, cancellations and refunds. We strongly dispute any suggestion to the contrary,” said Jennifer De La Cruz, a spokesperson for Frontier.

In June, De La Cruz told the FOX31 Problem Solvers that passengers who were issued a credit during the COVID-19 pandemic were given 90 days to use their credit to book another reservation.

“Note that travel does not need to occur within the 90-day period,” she said. “Travel can occur anytime through the end of the airline’s published schedule which currently runs through September 2021. Additionally, Frontier’s standard change policy allows customers to change their reservation for free outside 60 days of the scheduled date of travel.”