On the DOT site it has this text so it does look like DOT has something to say on this matter. The way I am interpreting it, if the airline has issued a refund then the OTA has to issue that same refund to the consumer within 7 days. If the airline has NOT issued a refund then the OTA DOES NOT have an obligation to grant a refund to the consumer meaning that the refund regulation is toward the airline and not the OTA independently. However, I do not think the OTA can just keep the money if the airline has infact issued the refund.

The text here is "owed a refund"... if the airline has issued a refund then the passenger is "owed a refund". Hence, the text quoted below applies - if the passenger is "owed a refund" the OTA must process it within 7 days.

https://www.transportation.gov/indiv...ection/refunds

How quickly is an airline, travel agent, or online travel agency required to process a refund?

• If a passenger is owed a refund, an airline, travel agent, or online travel agency must process it within seven business days if the passenger paid by credit card, and 20 business days if the passenger paid by cash or check.