SEATTLE (AP) — Alaska Airlines says it is taking precautions including requiring employees to change their passwords after Virgin America’s computer systems were hacked.

An Alaska Airlines spokeswoman said Monday that the company noticed unusual activity in Virgin’s systems in March and notified law enforcement and hired cybersecurity experts. She said customer information wasn’t affected but employees and contractors will be required to change passwords every 90 days.

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Alaska bought California-based Virgin America last year.

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A letter to Virgin America employees from Kyle Levine, general counsel of Seattle-based Alaska Air Group Inc., was posted on the California attorney general’s website last week.

Levine said the hacker or hackers gained employees’ login information and passwords to Virgin America’s network. He offered advice for employees who think they might be victims of identity theft.

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