Britain's third largest tour operator, the XL Leisure Group, went into administration overnight leaving 85,000 holidaymakers stranded.
Some passengers flying to Greece and Spain from Dublin airport today were affected.
Last month, two companies - a tour operator based in County Mayo and a budget airline - collapsed leaving hundreds of passengers stranded.
All flights operated by XL have been cancelled and its planes have been grounded. Two return flights operated by XL were due out from Dublin airport today to Reus in Spain this morning and Skiathos in Greece this afternoon.
The Commission for Aviation Regulation says it has organised alternative flights for passengers due to travel back to Dublin from Skiathos in Greece tonight with XL. They will now arrive back in Dublin after midnight.
The Commission has also confirmed flights for passengers due to fly with XL back from Bourgas in Bulgaria to Dublin and Knock on Monday.
It says tour operator Sunworld is working to find alternative aircraft to replace the XL flights its customers were due to use tomorrow and Sunday.
The Civil Aviation Authority (CAA) in Britain said it was working with the travel industry to bring tens of thousands of stranded holidaymakers home.
It estimated there are 50,000 customers on holiday who booked through an XL tour operator, 10,000 on holiday with XL Airways, and 25,000 with other tour operators who shared the XL flights. A further 200,000 customers have advance bookings with the XL tour operators. The CAA advised passengers with advance bookings not to go to their departure airport.
The XL Leisure Group declared bankruptcy early today, having failed to secure a rescue package amid deep financial difficulties. In a statement on its website, the group said it had been hit by rising fuel costs and the credit crunch.
