Stansted Airport has apologised "unreservedly" after problems with its meet and greet parking system meant some passengers had to wait more than a day to get their cars back.
Customers reported "chaos" as they waited for hours, only to be told their vehicle or keys could not be found.
As reported in The Daily Mail, the airport blamed "technical issues".
"It's just incredibly poor customer service," said Jon Reason, one of the passengers affected.
He and his young family arrived back at Stansted from a two-week holiday at 00:30 BST on Sunday to be told their vehicle would be returned to them within two hours.
"It was just chaos - there were people queuing out the door. People were very irate, sitting on grass mounds just waiting for news," he said.
Eventually Mr Reason was informed by staff that his car could not be found, and was forced to wait for another two hours for a taxi back to his home in Billericay, Essex.
The performance of our Meet & Greet has fallen well below the standards we strive to provide, and for this we sincerely apologise. 1/2 pic.twitter.com/TKYnCM4DdI— Stansted Airport (@STN_Airport) August 7, 2017
The family's car was eventually brought back to them on Tuesday evening.
"No-one's putting their head above the parapet - I'm surprised Andrew Cowan, the CEO, hasn't come out personally and said 'we're not very good at this'," Mr Reason said.
"I'd never use the meet and greet parking again."
A spokesman for Stansted Airport said its "car parking operations suffered a number of unforeseen issues" on 5 August that caused "significant disruption".
He said "extensive recovery plans" had been put in place, including allocating arriving customers to different onsite car parking and arranging complimentary taxis to minimise disruption.
"The performance of our meet and greet service has fallen well below the standards we strive to provide our customers, and for this we sincerely apologise," the spokesman added.