“The Department has received an unprecedented volume of complaints from passengers and is examining this issue closely to ensure that airlines’ policies and practices conform to DOT’s refund rules,” said Secretary Chao. “The Department is asking all airlines to revisit their customer service policies and ensure they are as flexible and considerate as possible to the needs of passengers who face financial hardship during this time.”

In April, the agency warned airlines that they are required to provide a refund to travelers if their flight is canceled or significantly changed by the airline.

Because “cancellation” and “significant change” are not defined in the context of ticket refunds, airlines may develop reasonable interpretations of those terms, the DOT said in the enforcement notice.

"However, the Aviation Enforcement Office expects carriers to honor those reasonable interpretations in implementing their refund obligations and will focus its enforcement actions on instances where a carrier has disregarded the requirement to offer refunds, failed to honor its refund policies, or where it is determined that the carrier’s refund policies or practices are otherwise “unfair or deceptive,'' the DOT said.