Excerpt:

Air Canada says the personal information for about 20,000 customers "may potentially have been improperly accessed" via a breach in its mobile app, so the company has locked down all 1.7 million accounts as a precaution until customers change their passwords.

The airline told customers in an email that it "recently detected unusual log‑in behaviour with Air Canada's mobile App between Aug. 22‑24, 2018."

The company estimates about one per cent of the 1.7 million people who use the app may have been compromised.

The app stores basic information such as a user's name, email address and telephone number, all of which could have been improperly accessed.

Any credit card information on file would have been encrypted and as such protected, the company says. 

But additional data such as a customer's Aeroplan number, passport number, Nexus number, known traveller number, gender, birth date, nationality, passport expiration date, passport country of issuance and country of residence could have been accessed, if users had them saved in their profile on the app.