British Airways passengers have expressed their anger at being unable to get through to the airline following the confusion over cancelled flights.
BA pilots are due to strike on 9, 10 and 27 September - but BA also told customers with tickets booked on other days that their flights were cancelled.
The company admitted on Saturday that it had told some passengers, by mistake, to rebook or get a refund.
It said those who booked other flights could claim the extra costs back.
However, it has not commented on how many customers have been affected, or the reason for the error.
BA also said it received nearly 40,000 calls in the first 24 hours and was working around the clock to help fix people's problems.
After initially sending one email informing customers of cancellations - telling them to rebook or seek refunds - BA then sent a second email to some people saying their original flights would go ahead as planned.
But in the second email, passengers were not given a link to automatically rebook onto their original flight, meaning they had to contact BA directly.
Some customers say they have spent hours trying to get in touch with BA's customer services without success.
Allow Twitter content?
One woman, Josie Simpson, told the BBC she called the airline 67 times to try to rebook a family holiday to Florida.
The company's Twitter feed has also been inundated with messages from frustrated people.
Allow Twitter content?
In response to one passenger, a BA representative said: "We're extremely sorry that you're having difficulties trying to rearrange your flights.
"Our teams have been working tirelessly to help as many of our customers as possible, in these unprecedented circumstances."
Analysis: A mess of BA's own making
By Katy Austin, BBC News business correspondent
This has not been a good bank holiday weekend for British Airways - but this was a mess of the airline's own making.
From the moment it made the mistake of sending out emails cancelling flights that it didn't mean to cancel, it has repeatedly left customers hot and bothered. People who would have preferred to be enjoying the August sunshine have instead been spending hours trying to phone the airline to understand what is going on.
Communication does appear to be the issue here - and although BA has apologised, it has yet to explain how those erroneous emails came to be sent.
The airline's communication team has been very keen to send us statistics to show how many staff it has brought in to deal with the problems - and has today reassured those panicking about planned trips that any extra costs would be covered.
But that reassurance has limited effect while people still can't get through on overwhelmed phone lines.
Some affected passengers have told the BBC they will never again book with BA. It's a sign of the trust that's been lost during a scorching bank holiday weekend when BA has certainly been feeling the heat.
Some customers who were told their flights were not scrapped after all have been left confused about whether their decision to accept a refund has now been cancelled.
Others said they fear being left out of pocket.
Ellie Kormis, from Surrey, spent the whole of Saturday trying to speak to BA after being told one of her flights for her family's package holiday to Greece was cancelled.
She said they ended up booking new flights - which extended their holiday by three days - and extra accommodation, costing more than £2,000.
"You're left in a situation where you can't speak to anyone - and you fear you'll either lose your holiday or be left out of pocket," she said.
BA then contacted her by email to say her flight wasn't cancelled after all.
She said it was "an epic mess up on their part", joking that she had lost hope she would ever get through to speak to someone at BA, having made over 70 calls.
A BA spokeswoman said customers who were told their flights were cancelled in error and had booked alternative flights or incurred other expenses would be entitled to refunds if they submitted receipts.
Earlier, some people said they were told that wasn't the case.
Kaelee Matthews, from Cardiff, said BA had told her it wouldn't give her a refund for her flights to Orlando - which the airline had initially said were cancelled - because they were still operating.
She has booked new flights with Virgin for her and her partner - costing an extra £440 in total.
"We are disgusted with BA," she said. "We don't know what to do now. Virgin can't refund us, but we understand that. Travel insurers say we're not covered either."
Laura Gillespie, 48, from Perth, was also told by BA she was no longer entitled to a refund as her flight from London to Edinburgh was going ahead after all.
"I've now got flights booked with two different airlines going to the same place and I'm £140 down," she said.
"I know it's not a lot of money compared to some folk who have spent thousands but it's so annoying."
In response to customers being frustrated at not being able to get through to customer services, BA said:
- It received 38,000 calls and 33,000 tweets in first 24 hours
- Contact centres stayed open 24 hours to help resolve issues, with 70 extra staff
- Around 100 staff were working to answer Twitter queries
The British Airline Pilots Association (Balpa) said on Friday the strikes were a "last resort" born out of "enormous frustration" with airline management.
Pilots have rejected a pay increase worth 11.5% over three years, which the airline put forward in July.
BA says it carries 145,000 customers every day - with a fleet of more than 280 aircraft - and a BA plane takes off from somewhere in the world every 90 seconds.
What can I claim if my flight has been affected by the strikes?
BA advice says you can request a full refund, rebook your flight for another time in the next 355 days, or use the value of your fare to fly to a different destination.
If your flight has been cancelled because airline staff are striking, the the Civil Aviation Authority said, then this would be considered within the airline's control, and therefore you have a legal right to either:
- A full refund, and this includes flights in the same journey that might be from a different airline (for example, an onward or return flight)
- A replacement flight to get to your destination
- Or, if you are part way through your journey and don't want a replacement flight, you are entitled to a flight back to the airport you originally departed from
In some cases, passengers may be entitled to additional cash compensation for the inconvenience - but only if you receive notice that your flight is affected less than 14 days before departure.