Airlines must fully refund airfare to passengers whose flights have been canceled during the outbreak of COVID-19, the U.S. Transportation Department ordered on Friday.

It is receiving a growing number of complaints from people who say airlines have refused to pay refunds after flights were canceled, the agency said in a press release and an enforcement notice.

“The obligation of airlines to provide refunds, including the ticket price and any optional fee charged for services a passenger is unable to use, does not cease when the flight disruptions are outside of the carrier’s control,” the agency said.

The directive applies to domestic and foreign airlines for flights to, within, or from the U.S. It applies when an airline “makes a significant schedule change and the passenger chooses not to accept the alternative offered by the carrier,” according to the department.

The order threatens to add more financial strain to an industry that is facing severe challenges from a dramatic plunge in demand even as it prepares to start receiving US$50 billion in loans and payroll assistance payments contained in a government bailout package.

As of Thursday, passenger traffic had fallen about 95 per cent compared with a year ago, according to the Transportation Security Administration. Only 124,021 passed through security that day compared with 2.4 million on the equivalent weekday in 2019.

In response, airlines have canceled thousands of flights a day and cuts are expected to remain for weeks or longer.

Instead of giving passengers their money back, they have been told by airlines they would only receive vouchers or credits for future travel, the department said in the release.

The rules requiring refunds have been in place for decades, according to DOT. They have been enforced after previous disruptions to the aviation system, such as the Sept. 11, 2001, terrorist attacks and Hurricane Katrina in 2005, the agency said.

The trade group for major carriers, Airlines for America, issued a statement Friday saying its members are working closely with the government and Congress during the virus emergency.

“Since the early stages of the crisis, carriers have worked to increase communications with customers, as well as introducing travel policies to accommodate passengers during this health crisis,” the group said in a statement.

The trade group didn’t directly address the extent to which U.S. airlines have been unwilling to make refunds or whether any carriers are changing their policies.

Initially, the government is giving airlines the opportunity to comply with the law on their own, the Transportation Department said. “However, the Aviation Enforcement Office will monitor airlines’ refund policies and practices and take enforcement action as necessary,” it said.