British Airways, United Airlines Holdings Inc. and Singapore Airlines Ltd. were among carriers affected by a cyberattack that hit the Star and Oneworld alliances, exposing some loyalty-program member information.

SITA Passenger Service System Inc.’s processing services were hit by a “highly sophisticated but limited” breach that targeted personal data stored on servers at its data center in Atlanta, the company confirmed in an emailed statement. The problem was identified on Feb. 24, and the hackers were able to access the data for less than a month, it said. SITA PSS is a unit of SITA Group, a closely held…