The hack of a company that manages ticket-processing and frequent-flier data for major global airlines � including Star Alliance and OneWorld members � has compromised the personal data of an unspecified number of travelers.

The hackers were able to access some computer systems at Atlanta-based SITA Passenger Service System for up to a month before the incident�s seriousness was confirmed on Feb. 24, a spokesman for the company�s Geneva-based parent company said.

The spokesman, Sandro Hofer, would not say how many airlines were affected � SITA says it serves more than 400 and is industry-owned. The company said that Singapore Airlines, New Zealand Air and Lufthansa were among those affected.

�The extent to which (frequent flyer alliances�) individual airlines were affected varies from airline to airline,� SITA said in a statement.

It said Malaysia Airlines, Finnair, Japan Airlines, Cathay Pacific had either issued statements or reached out to frequent-flyer members about the hack.

United Airlines said separately that the only customer data potentially accessed were names, frequent-flyer numbers and program status. It recommended in an email that frequent-flyer customers should change their account passwords �out of an abundance of caution.�

SITA provides IT services for the airline industry, including passenger travel planning and booking, airport operations and security, baggage, aircraft connectivity and in-flight cabin and cockpit operations. It first announced the breach on Thursday.

(AP)