Thousands of holidaymakers are still owed tens of millions of pounds through outstanding claims following the collapse of Thomas Cook.
The UK Civil Aviation Authority (CAA) said more than 250,000 claims – about 75% of the total received – have been settled through the Atol financial protection scheme it manages.
It has resulted in payments of more than £200 million since Thomas Cook went bust in September.
CAA chief executive Richard Moriarty said the regulator was in the process of undertaking the UK’s “largest and most complex” travel claims operation.
He said delays with processing the remaining claims were due to the “quality of information” received from Thomas Cook’s systems and the risk of scams.
It comes as the Insolvency Service said £585 million was owed to customers for package holidays, flights and other services after the firm collapsed.
A CAA spokesman said Atol is only refunding Thomas Cook’s package holidays and not flight-only bookings.
Mr Moriarty said: “We want to ensure we get the right amount of money back to the right people as soon as we can, and we have so far paid out over £200 million by settling over a quarter of a million claims, 75% of the total we have received.
“We understand that those consumers that have not been paid yet have had to wait longer than we had hoped and we are doing all we can to process these claims as soon as possible.
“Unfortunately, our operation has had to include extra checks and processes owing to the quality of the information we received from Thomas Cook’s systems and the potential threats of scams and fraud.”
The claims process opened on October 7 and will remain open until September 22 2020, the CAA said.
Trade creditors such as hoteliers, airports and aircraft catering suppliers were owed £885 million following Thomas Cook’s demise.
Total liabilities for Thomas Cook Group were around £9 billion, with the majority owed to other companies within the group, including some which have ceased operations.
The Insolvency Service said it is not known how much of the money will be paid back as a result of Thomas Cook’s liquidation.
Some 300,000 of the cancelled holidays are financially protected under the Atol scheme, although earlier this month the CAA said around one in three of the first people to claim refunds were not paid within the 60-day target.
The regulator insists it wants to issue refunds “as soon as possible” but said some cannot be paid until additional information is provided by claimants.
Business Secretary Andrea Leadsom added: “It is totally unacceptable and irresponsible for companies to reward mismanagement, with huge bonuses for directors who fail in their duty of care to employees and creditors.
Many Thomas Cook customers have taken to social media to express their frustration over the time it is taking to get their money back.
Dale Edwards wrote on Twitter: “Day 67 still no refund. All information sent to Protect Claims.”
He added: “Really getting annoyed now.”