More than 10,000 Monarch passengers who were abroad when the airline collapsed are due to return to the UK on Thursday as efforts to repatriate thousands of holidaymakers continue.
The Civil Aviation Authority (CAA) said so far 173 flights had brought back 34,608 people, with another 10,793 expected to return on 58 flights on day four of the operation.
The remaining 75,392 Monarch Airlines customers are expected to be back in the UK by October 15.
The CAA and the Government said they are working around the clock to deliver the biggest peacetime repatriation, which was prompted by the airline going into administration and cancelling the flights and holidays of 860,000 people.
On Wednesday it was revealed Unite the union would begin legal action on behalf of more than 1,800 Monarch airline workers who lost their jobs.
Dame Deirdre Hutton, chair of the CAA, said the operation remains on course.
She said: "Our operation has thus far gone well and I am very pleased with the progress we have made during the first three days. However, this is a huge undertaking and we still have 11 days to go. Everybody at the CAA remains completely focused on this mission.
"Like any other airline, some of our aircraft have experienced delay, due to both technical faults and bad weather, resulting in frustration for some passengers.
"We have also been in contact with more than 2,200 hotel and accommodation providers, giving them financial guarantees and ensuring Atol-protected customers can continue their holidays unhindered. We will continue to work with hoteliers should there be any further concerns."
Administrators KPMG said 1,858 of around 2,100 people employed across Monarch's airline and tour group had been made redundant after the firm went bust.
Ninety-eight of those made redundant were employed by Monarch Travel Group, while 1,760 worked for Monarch Airlines. The remaining employees will help with the administration process, and assist the CAA in bringing holidaymakers abroad back to the UK, KPMG said.
Administrators are now considering breaking up the company, which was founded in 1967, as no buyer has been found to purchase Monarch in its entirety.
The group's engineering operation, Monarch Aircraft Engineering Limited, is not in administration and continues to trade normally.