Thomas Cook customers have told the BBC of their fears over unpaid hotel bills, cancelled trips and being stranded abroad following the collapse of the tour operator in the early hours of Monday morning.
For one British family on holiday in Cyprus, the firm's failure means a wedding marred by uncertainty, and worries over vital medication.
Grandmother Mary Nichols, 87, has a heart condition and only enough medication to last until Wednesday - the day her prescription runs out.
Grandson Matt Walker, 23, paid Thomas Cook about £1,100 by debit card for flights and hotel accommodation for Ms Nichols and his mother Sarah, 53, so they could attend his brother's wedding in Paphos on Tuesday.
But the family's excitement has turned to fears they could be stranded, after staff at the Kefalonitis hotel apartments said Thomas Cook had not yet paid for their stay.
Mr Walker, from Poynton, in Cheshire, said: "We are unsure what to expect from the hotel. They've got our passports and told us they have not been paid by Thomas Cook.
"We're the only Thomas Cook passengers here, and they're not taking any more. We're not sure if they [the hotel] wants extra money.
"My nan fears if she's stranded in Cyprus she will run out of the medication she must take daily. She has her medication until Wednesday - even a delay of one day is trouble."
The family have been given no information about whether flights home will go ahead.
Mr Walker said he fears he will not be able to enjoy his brother's wedding because of the uncertainty.
He said: "We feel left in the dark - the hotel doesn't know what's going on, there's no Thomas Cook rep and Thomas Cook haven't contacted us.
"I am going to have to make phone calls on my brother's wedding day tomorrow and get it sorted out. It's going to ruin the day because I'm going to be on the phone when I should be enjoying myself."
Wasted gift vouchers
Back in the UK, mum Leanne Jones has been forced to tell her children that their planned trip to Disneyland Paris in June has been cancelled.
Ms Jones, from Milton Keynes, said she feels "rubbish" after learning £800 worth of Thomas Cook gift vouchers saved for her two young sons' first foreign holiday are worthless.
Ms Jones said the family were £150 off meeting the £2,300 cost of the trip after separately putting money into a holiday fund.
She said she and her partner, Andy, held off booking the holiday until they had the necessary funds.
She said: "Every birthday and Christmas over the last two years I've been saving to take my two young children [Harrington and Hudson] on their first holiday abroad - Disneyland Paris was the plan.
"We just thought it would be magical for them.
"I stand to lose all the money from the vouchers and my children will no longer get their holiday. After speaking with Atol [A scheme that protects most air package holidays sold by businesses based in the UK] I've learned my vouchers are not covered and there is nothing anyone can do to help.
"I'm going to have to start saving again - I have no other option. We'll have to wait another two years."
The Civil Aviation Authority, which runs the Atol scheme, has been contacted for comment about the status of gift vouchers.
Memorial service doubts
For Zoe Sheehan, 36, from Wales, the travel giant's collapse means she and her husband may miss a family memorial service in Gran Canaria.
Mrs Sheehan and Stefan, 28, spent months planning the trip to scatter her father's ashes.
They are now searching for new flights but do not know when they will be reimbursed for the old ones as there is no word from their travel insurer.
The couple drove to Gatwick in the early hours of Monday in the hope they could book alternative flights.
Mrs Sheehan said: "I won't stop trying until my last breath. We're shopping around now for flights, but they're so expensive.
"We had planned this [trip] for months. We have insurance and we have paperwork for his ashes.
She added: "It's really important not just for us two, but our two children and my mother.
"The kids are coming down with their Nan and they're just crying. I was crying earlier."
Dream job over
Ella Waine said passengers told her she had lost her "dream job" when they saw the news of Thomas Cook's collapse on their mobile phones after their plane landed.
Miss Waine, a seasonal member of Thomas Cook's cabin crew, had flown to Hurgada, in Egypt, while discussions to save the company were on-going.
But when their plane arrived back at Birmingham airport, passengers received news alerts of the company's collapse and told her and other staff.
Miss Waine, from Broughton Astley, in Leicestershire, told the BBC: "It was a complete heart-to-the-stomach moment.
"We found out at exactly the same time as the passengers.
"An email was sent out to our company emails but we can't go on our phones whilst we were on the flight."
The 19-year-old said she was "devastated" to lose her "dream job", and that staff did not know whether they would be paid at the end of this month.
Miss Waine said she had work lined up for when her contract ended in November, but now needs to find a job urgently until then.
'Asked to pay'
Hours after landing in Fuerteventura, Sam Emerton and partner, Shaylee, were told they must pay €1,211 (£1,071) to stay in their hotel after their booking was cancelled in the collapse.
Staff at H-10 Ocean Suites, initially told the couple they would only have to pay €173 (£153) for one night's stay while the CAA resolved the situation.
But the pair from Milton Keynes, in Buckinghamshire, say the CAA has now told them they must pay the full hotel bill of €1,211 (£1,071) because their flight departed from Gatwick at 05.45 GMT - hours after Thomas Cook announced it had gone into administration shortly after 02.00 GMT.
But Mr Emerton, 24, insists they received no communication from Thomas Cook to tell them the company had gone bust- and they first learnt of it on landing in the Canary Islands.
The couple had been paying Thomas Cook £330 a month since March for the all-inclusive package holiday - which included Easyjet flights.
He told the BBC: "We drove to Gatwick at 1:30 in the morning, unbeknown to us that Thomas Cook has collapsed.
"No-one told us. We received no email or text message from Thomas Cook.
"Our flight landed [in Fuerteventura] and we got our bags, only to be greeted by no-one. The Thomas Cook stand was empty.
"About half an hour later a woman showed up to tell us Thomas Cook had gone bust, there were no transfers to the hotel and the hotel would not accept us unless we paid 1,211 Euros."
Mr Emerton says the couple borrowed the money for one night's stay from Shaylee's dad, but do not have the money to pay the full bill.
The CAA has been contacted for comment in relation to the couple's case, and says it will investigate.