Department of Transportation is seeking $25 million from Air Canada for what it calls "extreme delays" in refunding tickets to Americans who booked tickets on flights that the airline never flew.

The department said in a release on Tuesday that its Office of Aviation Consumer Protection (OACP) has launched a formal complaint against the airline due to the carrier's "failure to provide refunds in a timely manner to thousands of consumers who requested them for flights to or from the United States that the carrier cancelled or significantly changed.".

According to the release, the agency has heard from more than 6,000 of the airline's American customers, who said they had to wait anywhere from five to 13 months to get their money back from flights that were cancelled.