Thomas Cook holidaymakers have begun arriving at Cardiff Airport after being caught up in the collapse of the travel company.
The airport estimates nearly 6,000 passengers have travelled on flights with the package holiday operator in the last couple of weeks.
Thousands more Welsh travellers have been hit at flight hubs in Manchester, Bristol, Birmingham and London.
In Wales, 28 high street travel shops have also closed.
Kelly Probert-Wilmott from Newport arrived at Cardiff Airport from Zakynthos in Greece on Monday evening.
She said: "It's been a bit traumatising for the kids but to be fair the hotel helped us and looked after us.
"We didn't know what the flights were going to do or if we were going to get home, it could have been a week or two weeks.
"It's been emotional because we've seen the crew members upset… very, very emotional."
Rhia Presley and Jason Forsyth from Cardiff are due to take their three children, aged 11, nine and six, on holiday to Disney World in Florida.
They spent more than £4,000 on Thomas Cook flights in August using a debit card and are waiting to hear if they can get their flights refunded after making a transaction dispute with their bank.
"When you're disappointing your children that's what makes it worse," said Ms Presley.
"Thomas Cook has been around for so long we didn't think there'd ever be a problem."
The couple are getting married in July and had planned the trip instead of having a honeymoon.
"I'm quite angry really," said Mr Forsyth.
Rob Barrett from Porth, Rhondda Cynon Taff, is in Paphos in Cyprus for his daughter Yasmin's wedding after booking accommodation and flights through Thomas Cook.
He said when his mother-in-law arrived on Monday she had to pay £1,300 for her accommodation despite having paid for it over a year ago.
He said he witnessed a bride leaving the wedding venue in tears on Monday morning after no-one turned up to carry out the ceremony.
"She was in her wedding dress and the groom was there too," he said.
"They were there for an hour or so but the wedding planner had been told not to turn up for work."
Mr Barrett flew out with his wife and son, 11, on Friday from Bristol and is due to return home on 4 October.
"There's a lot of chat obviously but no-one knows what's going on," he said.
"We don't know how we're getting home or if we'll be charged to stay here… it has spoiled things."
He is optimistic his daughter's wedding will go ahead on Wednesday as it has been arranged by a local wedding planner.
Cardiff Airport's Chief Executive Deb Bowen Rees said: "We've had about 5,800 passengers depart with Thomas Cook from the airport over the last couple of weeks.
"Between now and the end of the season in the end of November, we had about 120 flights scheduled to depart and that would impact about 24,000 customers."
The airport boss said airline operators in particular had been facing "volatile times".
"Fuel prices, currency, the uncertainty of Brexit - all that kind of thing - are impacting on airlines," she said.
The airport has warned those booked onto Thomas Cook flights from Cardiff "not to travel" to the airport, and seek advice from the Civil Aviation Authority (CAA), which has been co-ordinating the UK response to the travel firm's collapse.
The airport said flights operated by TUI and Vueling Airlines were continuing as normal.
"We would like to reassure customers that we will do our utmost to support in the repatriation efforts, and we will continue to work closely with the Civil Aviation Authority to facilitate arrangements for any customers affected by this news," added Ms Bowen Rees.
The travel firm's collapse came after last minute negotiations to save the 178-year-old company failed.
An estimated 150,000 holidaymakers from the UK are thought to be abroad with Thomas Cook flights and hotels.
The tour operator's failure puts 22,000 jobs at risk worldwide, including 9,000 in the UK.
Wales' Economy and Transport Minister Ken Skates said he was liaising with the UK government and the Welsh Government would work to support those at risk of losing jobs.
Holidaymaker Sophie Rees, from Swansea, was caught up in the collapse of Thomas Cook - even before the firm went bust overnight.
The 24-year-old was at a hotel in Tunisia over the weekend, where she and other guests were barred from leaving and told to pay again for their holiday.
"On Saturday, everyone who was leaving that night was called to reception and basically told to pay for their holidays as they didn't think they were going to get any money from Thomas Cook," Ms Rees told BBC Radio Wales Breakfast.
"We refused to pay them - because we had already paid. But they managed to get about £2,500 off an elderly lady, which we thought was pretty despicable, to be honest."
She said guests tried to leave the Les Orangers Beach Resort but found gates "barricaded" with glass shards on walls making it impossible to leave.
"We hadn't had any advice, we had no idea what was going on," she added.
"It was pretty horrendous - it was a pretty scary situation - it was very volatile."
Ms Rees said staff from Thomas Cook eventually arrived at the resort after about a three-hour wait, and payments were made to the hotel, allowing them to leave.
Now back home in Wales, Ms Rees said she was concerned for those still at the hotel complex, after the firm's collapse.
Analysis from Brian Meechan, BBC Wales business correspondent
Everyone's thoughts today are with the staff and customers of Thomas Cook.
The management of Cardiff Airport will be focused on its role in the CAA's operation to get people home.
But it will also have to start looking to the future soon.
With about 100,000 Thomas Cook passengers flying from Cardiff Airport a year, it will be trying to secure other airlines to provide routes for those customers in 2020.
Arranging that in time for the summer season next year could be challenging.
However the airport will at least be able to show that the demand is there.
Christopher Stephens, from Gabalfa in Cardiff, was waiting outside a local branch of Thomas Cook from 09:30 on Monday morning.
He had paid £460 deposit on a holiday to Tenerife next year.
But without an internet connection at home, he said he did not know what happened next.
"I'm retired - it's the only holiday we have, once a year, and we were really looking forward to it.
"That's why I've come down here today, to see if I can resolve the problem or what advice - what have I got to do to sort it out?" said 61-year-old Mr Stephens.
"We've been with Thomas Cook for 22 years. They are good staff - my heart goes out to them - I feel very, very sorry for them."
Don Bircham is managing director of Hayes Travel in Wrexham which sells Thomas Cook holidays.
He said: "It's been a challenging day. We've got over 2,500 bookings... staff are flat out trying to get people re-booked with alternative tour operators...
"We got wind of it about two o'clock last night so we've been in preparation since four o'clock this morning… I have to say the customers have been really, really cooperative and very, very good."
He said it could take his company up to two weeks to get customers booked onto alternative holidays.
The UK government has chartered 45 jets to bring customers home and they will fly 64 routes on Monday, in an undertaking dubbed Operation Matterhorn. The size of the fleet will make it temporarily the UK's fifth-largest airline.
Operators including easyJet and Virgin have supplied some aircraft, with jets coming from as far afield as Malaysia.
Customers can visit the CAA's special Thomas Cook website. Those scheduled to return to the UK within the next 48 hours or who are having problems with their accommodation or need special assistance can ring 0300 303 2800 in the UK or +44 1753 330 330 from abroad.