Manchester, London Stansted and East Midlands airports in the United Kingdom have been hit by a cyber-attack that exposed the personal data of about 8.7 million customers.

Manchester Airports Group, which operates the three airports, said the breach affected data linked to car park, lounge and fast-track bookings, as well as in-airport Wi-Fi registrations.

In an email to customers, London Stansted said, “We would urge you to be particularly cautious of unexpected emails, calls or text messages claiming to be from us. We will never contact you unexpectedly to ask for payment or banking information. We apologise for any inconvenience or concern this may cause.”

The cyber-attack occurred during the peak summer travel season, with many families returning to the UK this week ahead of the new school year. Manchester, London Stansted and East Midlands airports handled a combined 54 million passengers last year.

A spokesperson for Manchester Airports Group said the company had “immediately contained the risk” posed by the incident and was “working with specialist advisers and taking appropriate steps to protect our customers and systems”.

The compromised data included customers’ email addresses, phone numbers, vehicle registration numbers and postcodes.

MAG said the incident did not compromise passenger safety or aviation security, while airport operations continued unaffected.

The group also confirmed that the affected system did not contain customers’ bank or payment details.

“We have informed and are working with the relevant authorities. At no point has passenger safety or aviation security been compromised,” they said.

“Airport operations remain unaffected and customer parking services continue to operate normally.

“We would like to reassure customers that Manchester Airport Group takes the security of customer information extremely seriously and we apologise for any inconvenience or concern caused.”

The incident comes amid growing pressure on suppliers and operators of critical national infrastructure to strengthen their cyber-defences.

Last year, flights were delayed and cancelled at three major European airports, including London’s Heathrow, after the company providing software for check-in and boarding services reported a cyber-attack.

Earlier this month, hackers linked to Iran were blamed for an attack that temporarily shut down a British power plant. The government said the incident affected a small-scale generator and did not pose any threat to the wider energy system.

The UK also experienced a wave of high-profile cyber-attacks against major companies last year.

The incidents included an attack that disrupted Jaguar Land Rover’s operations for weeks, as well as breaches targeting Marks & Spencer, Harrods and the Co-op food chain.