Manchester Airports Group (MAG) — a public-private partnership which operates three of England’s busiest airports — said Thursday it was hit by a cyberattack affecting data belonging to about 8.7 million customers.

According to the company’s announcement, an unauthorized third party recently accessed customer data associated with car park, lounge and Fast Track bookings, as well as in-airport Wi-Fi sign-ups at the Manchester, London Stansted and East Midlands airports.

MAG did not disclose how the attackers gained access to the relevant system, nor did it set out what the attackers did while inside beyond accessing customer data. The three airports handled more than 65 million passengers last year, although not all of these would have interacted with the affected services.

The compromised information includes email addresses, phone numbers, vehicle registrations and postcodes. The company said neither it nor the affected system stores customers’ bank or payment card details and that no financial data was exposed.