Holidaymakers and families hoping to get away for the long weekend or school break were met with chaotic scenes at London terminals.
Scores were left stranded after British Airways grounded all planes from Gatwick and Heathrow on Saturday because of a global problem with its IT systems.
BA's Twitter page was flooded with questions from frustrated customers desperately looking for information about what was going on.
Several passengers at Heathrow told the Press Association they had not been informed their flights were cancelled until more than an hour after the airline put out a press statement announcing the decision.
Terry Page, 28, from London, said: "There's no such announcement here. The boards are showing Go to gate, and no mention of cancellations."
More than an hour later, he said cancellations of individual flights were still being announced.
Footage filmed at the terminal showed long queues at customer services, after passengers had been advised that they would be unable to rebook due to systems remaining down.
Student Emily Wilson told the Press Association that she had been advised "we are unable to get bags, and that no more flights are taking off", several hours after having arrived at the airport for her flight to Stockholm.
Ms Wilson added: "We were told (it would be) about three hours for collecting bags, that all compensation will have to be done online, and that we are unable to rebook flights now because of the system being down."
She said that information on screens still suggested her flight could board shortly, but that staff contradicted that information, saying there were "no slots left".
Frustrated passengers could be seen calmly surrounding BA staff at the check-in at Gatwick airport.
Airline workers were handing out letters which apologised for the cancellations and gave details about how to claim for hotels, local transport and refreshments.
Bernadette Young, 38, from Farnham, Surrey, was travelling to Portugal with her husband Cris, 37, and daughters Beatrix, five, and Theodora, two, for their first family holiday in three years.
Mrs Young, who had been a teacher before becoming a stay-at-home mother, said: "We cannot get on a flight today and we have been offered a flight from Manchester tomorrow but we cannot drive up there.
"The girls are really disappointed. It is half-term and we have only got a week. They were looking forward to it and really getting excited about going swimming in the sun.
"Hopefully we will still be able to go."
Mrs Young said "it doesn't help to be hysterical about an unfortunate situation", adding: "Given what has happened this week in Manchester, this is not the worst thing in the world.
"I also think that if BA were not offering compensation, I might not be thinking that way. I think a lot of people are just giving up and cancelling."
Teacher Gemma Richardson, 30, who is 24 weeks pregnant, was travelling with her husband David, 30, and their two-year-old daughter to Spain.
Mrs Richardson, who was sitting uncomfortably on a barrier, said "it was chaos" when they arrived at the airport.
She said: "There was no formal guidance, just information on a screen saying that the flights up to 6pm had been cancelled.
"We all pooled around a BA employee who was doing her best to give advice.
"It seems that because it is a bank holiday weekend there is no spare flights. We are on standby but it is very unlikely we are going anywhere.
"It is all stressful but we are trying to put a best face on it for my daughter but it is very difficult.
"There are no real chairs here so I am sitting on a barrier which is not great."
Linda Murakami, 55, had flown in from her home in Pennsylvania, US, for a connecting flight to Naples, Italy, only to find it had been cancelled.
She is now cancelling a "dream holiday" to the Amalfi coast with her family.
Miss Murakami, who retired early from a pharmaceutical company, said: "This trip was my retirement present.
"There are a lot of other things that can cause disappointment and could put everyone in a worse situation.
"We just have to be flexible. We have travel insurance so feel that because we would miss part of the vacation, we might as well cancel it and just go again at a different time. For me, it is an inconvenience."
Her friend Joyce Cohen, of New Jersey, said: "This had been my dream vacation. Everything had been worked out so that I could come. I am very upset.
"I have waited for this my whole life and I am not in good health, so who knows what could happen by next year when I could come again."