In a joint open letter from the Competition and Markets Authority and Civil Aviation Authority, airlines were told the watchdogs are “concerned that consumers could experience significant harm unless airlines meet their obligations and minimise flight disruptions throughout the summer and beyond”.

The letter read: “It is critical that airlines take action to ensure consumers have a positive experience. Consumers must be kept informed of the status of their flights and made aware of their rights, so they can assess their options sufficiently in advance of travel.

“Where flights are cancelled, consumers should be supported and their rights upheld to ensure they get the best outcomes.”

The letter added that “some airlines have performed better than others” but stated they had concerns that several continue to sell more tickets than there are seats, aren’t giving customers sufficient notice when flights are cancelled and are failing to direct them to guidance on their legal rights.

The CMA and CCA told airlines: “We strongly advise you to make any necessary changes as soon as possible, to prevent further disruption and harm.”

If a flight is cancelled, customers are entitled to request their airline arrange and pay for them to take the next available flight to their destination, even if that is with a different airline. See YourMoney.com’s Flight cancelled or delayed? Your rights explained for more information.

Earlier this month, consumer group Which? said it had received multiple complaints from passengers who weren’t made aware of this rule, took compensation that left them out of pocket when they booked an alternative flight home, and some claimed they received no guidance at all from their airline following a cancellation.

Which? wrote to the CAA to highlight its concerns, naming both easyJet and British Airways in its correspondence.

‘Airline sector not been able to deliver’

Danni Hewson, AJ Bell financial analyst, said the airline sector “hasn’t done a great job” navigating its post-Covid return.

She said: “It wanted to take advantage of the surge in demand from consumers desperate for a foreign break – a bit of sun or a chance to reconnect with friends and family.

“But it has just not been able to deliver the kind of schedules required in time for those big holiday moments.”

Airlines have struggled with recruitment in the aftermath of the pandemic when thousands of pilots, cabin staff and ground staff were laid off after flights were all but grounded completely.

It has meant thousands of flights have had to be cancelled because there isn’t enough staff to operate them safely.

Last month, the Department for Transport and CAA wrote to airline and airport chief executives asking them to “review plans for the summer” to ensure expected passenger levels could be managed safely and minimise further disruption. Ministers subsequently implemented a slot amnesty programme to encourage airlines to remove flights from their schedules with no penalty.

Earlier this month Heathrow Airport told airlines not to sell any more flights departing before 11 September as it imposed an immediate cap on the number of passengers flying out to 100,000 a day.

Gatwick Airport set a daily passenger number cap several weeks before that.

Hewson added: “Images of queuing families, social media posts full of horror stories of people left stranded or getting cancellation emails on their way to the airport just hours before they were due to depart have left a bitter taste.”

The CMA and CAA’s letter cautioned that any repeat this summer could force them to take action, warning airlines they need to think ahead and take responsibility for customers who might not have the cash or the ability to get themselves where they need to go.

“Compensation must be paid quickly, and arbitrary limits shouldn’t be set on levels of compensation, plus travellers need to be kept well informed of cancellation policy and not find themselves struggling to pore over the small print,” Hewson said.

“It’s about transparency and boosting confidence, both things which are in airlines best interests.”