WestJet is notifying U.S. residents that their personal information may have been compromised in a cybersecurity incident first detected in June , the airline confirmed Monday.

The Calgary-based carrier stated that it identified suspicious activity on its systems on June 13 and subsequently determined that a “ sophisticated, criminal third party” had gained unauthorized access. While the airline stressed that its flight operations were never at risk, investigators confirmed that some data was obtained.

In a notice released on Monday , WestJet said it has completed an extensive analysis of the stolen data and identified U.S. residents whose information may have been exposed. The airline is now contacting those individuals directly and has posted additional guidance on its website.

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