British Airways has admitted it made a mistake when it advised passengers flights were cancelled and told them to book new ones.
Passengers have described "confusion" as cancelled flights were reinstated, but only after some of them rebooked.
BA apologised for any concern caused and said the email was an "error".
"We are getting in touch with all those customers this afternoon to clarify that their flight will go ahead as planned," a spokesman said.
"We are sorry for any confusion and inconvenience this has caused."
He encouraged anyone who had spent money on new flights to get in touch. "We will deal with each case on an individual basis," he added.
The airline announced that pilots would strike on 9, 10 and 27 September.
But on Saturday it told some passengers with flights between the 8th and 12th that their flights had been cancelled, and they should rebook or seek a refund.
Josh Sullivan, 27, from Trowbridge, had been due to fly with BA back to London on 8 September from his stag do in Prague.
He said his best man, who organised the flights, bought another pair of flights from Ryanair for £180 when he was emailed to say the flight had been cancelled.
BA has now informed him the flight has not been cancelled.
"The fact that they've un-cancelled it, we went through all this aggro today for no reason - and now I have two flights back from Prague and we're £180 out of pocket," Mr Sullivan said.
"It's a complete mess," he added.
BA explained there could still be some disruption to flights on 8, 11, and 12 September.
"Airlines have a very complex operation and during times of widespread disruption, there can be knock-on effect onto flights on other days," BA said.
It added: "We are doing absolutely everything we can to prevent this unfair action from taking place and ruining our customers' travel plans."
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.
Passengers described "utter confusion" on social media on Saturday.
Some said they had made alternative travel arrangements after being unable to get through to BA's customer services.
Josie Simpson told the BBC she called the airline 67 times to try to rebook a family holiday to Florida.
"We don't know whether we've lost the entire holiday," she said.
"It took us months to book, 18 months to save to pay for it... and it could all just be gone."
The airline is not expected to release details on how many people had been affected by the erroneous email.
@British_Airways I had an email to say flight on 8th September cancelled. Travel agent say they spoke to you and you said the email was an error. So is the flight cancelled or not? Do I need to rebook or not? This is a mess BA. Utter confusion for passengers— Molly Heckford (@madmolls) August 24, 2019
Chaos @British_Airways! Not our fault talks broke down with your pilots. You cancelled our flight & told us to rebook online. Well, we can’t (“Unknown Error”) &your phone lines are closed, have been for hours “We cannot connect you, pls try again later”. This is just unacceptable— أبو عمّار (@MaajidNawaz) August 24, 2019
@British_Airways You never answered me yesterday. You cancelled my flight on Sept 8th Miami to Heathrow. Finally spoke with Silver lune agent. Changed flight. Today new email - my original flight back on. WHAT ARE YOU DOING?? I’m not sure what my flight is! Systems chaos!!!!— Alina GarciaLapuerta (@GarciaLapuerta) August 24, 2019
Jonathan Greatorex, from Wrexham, bought new flights back from Marseille after spending "all day" trying to get through to customer services.
"The other flights are getting filled up, so I spent £600 booking alternate flights, only to get this email [explaining the error]," he said.
"I understand that the industrial action is outside of their control, however the complete omnishambles surely must rest firmly at their feet," he said.
"It's a complete and utter waste of money. I am absolutely furious," he added.
BA's Twitter feed was inundated with messages from frustrated customers, with some saying their cancelled flights were still on sale.
In response to one customer, BA said some flights before and after the strike were "still subject to disruption due to operational reasons, including crew rostering and positioning of aircraft".
Travel expert Simon Calder said two days of strikes had turned into five successive days of cancellations because BA would not send a flight to, for example, Hong Kong, if a pilot was going to go on strike the next day.
He also said BA has to find customers "an alternative flight on the same day if it possibly can, even if it means buying you a ticket on another airline".
If you are delayed overnight, he said BA has to pay for a hotel and meals.
He added: "The worst thing you can do is take a full refund because then you will be buying another ticket yourself and that could well cost more."
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.
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.