Frustrated holidaymakers have been waiting more than 40 hours to board a TUI flight from Cardiff Airport to the Greek island of Zakynthos.
Passengers on flights to Ibiza and Dalaman have also reportedly been delayed by more than 24 hours.
One passenger described the situation as a "comedy of errors" while others said there had been angry scenes caused by a lack of information.The flight to Zakynthos was due to leave Cardiff Airport at 2pm on Tuesday (May 24), but passengers were still waiting to fly out on Thursday morning.
They did board a flight at the airport on Wednesday evening, but were then taken off the plane after a health emergency.
TUI has apologised and said it has provided affected passengers with accommodation, food and drink, and the option cancel or amend their holidays if they wished.
One passenger, who asked not to be named, said: "We were supposed to fly on Tuesday afternoon, they told us it had changed to 4.30pm, then they announced about 5pm that we were rescheduling to next day .
"We had to get our cases back. No names were out on the coaches, and there was no checking of names when we got to the hotel in Cardiff north, where they were putting us up for the night.
"We came back to the hotel at 7am on Wednesday when they told us it was delayed to 12pm flight. They kept delaying it then finally we boarded at 5pm was on plane for two hours then they said that somebody was ill so had to be taken off the plane. They then told us that the plane couldn’t fly to Zakynthos as airport closes overnight.
"Passengers really upset refusing to leave plane at this point."
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Adam Crawley, from Carmarthenshire, has also been delayed. He said: "It’s been a comedy of errors by TUI from the start.
"I have seen elderly people in wheelchairs being loaded on and off buses to hotels for the past two days and shipped to hotels and back. The lack of communication has been farcical, completely pathetic."
Dylan Le Clare, who is also due to be on the flight, said: "When the flight was cancelled for a second time there was no sign of TUI members of staff anywhere. The lack of communication was very worrying."
A spokeswoman for TUI said: "As the UK’s biggest holiday company we will never cancel flights as we know how much our customers look forward to their holiday with us. We are doing everything we can to limit any flight delays, which can happen from time to time for various operational reasons. On the rare occasion flight delays do take place we will do everything we can to support our customers."We would like to apologise for the inconvenience to our customers travelling from Cardiff Airport today which have been delayed due to technical issues with an aircraft."Customers have been offered overnight accommodation where required, and meals and refreshments. They also have the option to amend or cancel their holiday if they no longer wish to travel."The safety and wellbeing of our passengers and crew is always our highest priority, and we would like to thank passengers for their patience and understanding at this time."
Spencer Birns, CEO at Cardiff Airport, said: “Please be reassured that the TUI and Cardiff airport teams are working exceptionally hard to assist customers and minimise disruption to passengers’ holiday plans. TUI has deployed a special assistance team to the airport, and it is working hard to advise customers of their revised departure times as quickly as possible”.